The Great Pyramid of Giza

It is the one and only Wonder which does not require a description by early historians and poets. It is the one and only Wonder that does not need speculations concerning its appearance, size, and shape. It is the oldest, yet it is the only surviving of the Seven Ancient Wonders. It is the Great Pyramid of Giza.


At the city of Giza, a necropolis of ancient Memphis, and today part of Greater Cairo, Egypt.


Contrary to the common belief, only the Great Pyramid of Khufu (Cheops), not all three Great Pyramids, is on top of the list of Wonders. The monument was built by the Egyptian pharaoh Khufu of the Fourth Dynasty around the year 2560 BC to serve as a tomb when he dies. The tradition of pyramid building started in Ancient Egypt as a sophistication of the idea of a mastaba or "platform" covering the royal tomb. Later, several stacked mastabas were used. Early pyramids, such as the Step Pyramid of King Zoser (Djoser) at Saqqara by the famous Egyptian architect, Imhotep, illustrate this connection.

The great pyramid is believed to have been built over a 20 year period. The site was first prepared, and blocks of stone were transported and placed. An outer casing (which disappeared over the years) was then used to smooth the surface. Although it is not known how the blocks were put in place, several theories have been proposed. One theory involves the construction of a straight or spiral ramp that was raised as the construction proceeded. This ramp, coated with mud and water, eased the displacement of the blocks which were pushed (or pulled) into place. A second theory suggests that the blocks were placed using long levers with a short angled foot.

Throughout their history, the pyramids of Giza have stimulated human imagination. They were referred to as "The Granaries of Joseph" and "The Mountains of Pharaoh". When Napoleon invaded Egypt in 1798, his pride was expressed through his famous quote: "Soldats! Du haute de ces Pyramides, 40 siècles nous contemplent". (Soldiers! From the top of these Pyramids, 40 centuries are looking at us)

Today, the Great Pyramid is enclosed, together with the other pyramids and the Sphinx, in the touristic region of the Giza Plateau. Also in the area is the museum housing the mysterious Sun Boat, only discovered in 1954 near the south side of the pyramid. The boat is believed to have been used to carry the body of Khufu in his last journey on earth before being buried inside the pyramid. It may also serve him as a means of transportation in his afterlife journey according to Ancient Egyptian beliefs.


When it was built, the Great pyramid was 145.75 m (481 ft) high. Over the years, it lost 10 m (30 ft) off its top. It ranked as the tallest structure on Earth for more than 43 centuries, only to be surpassed in height in the nineteenth century AD. It was covered with a casing of stones to smooth its surface (some of the casing can still be seen near the top of Khefre's pyramid). The sloping angle of its sides is 54 degrees 54 minutes. Each side is carefully oriented with one of the cardinal points of the compass, that is, north, south, east, and west. The horizontal cross section of the pyramid is square at any level, with each side measuring 229 m (751 ft) in length. The maximum error between side lengths is astonishingly less than 0.1%.

The structure consists of approximately 2 million blocks of stone, each weighing more than two tons. It has been suggested that there are enough blocks in the three pyramids to build a 3 m (10 ft) high, 0.3 m (1 ft) thick wall around France. The area covered by the Great pyramid can accommodate St Peter's in Rome, the cathedrals of Florence and Milan, and Westminster and St Paul's in London combined.

On the north face, is the pyramid's entrance. A number of corridors, galleries, and escape shafts either lead to the King's burial chamber, or were intended to serve other functions. The King's chamber is located at the heart of the pyramid, only accessible through the Great Gallery and an ascending corridor. The King's sarcophagus is made of red granite, as are the interior walls of the King's Chamber. Most impressive is the sharp-edged stone over the doorway which is over 3 m (10 ft) long, 2.4 m (8 feet) high and 1.3 m (4 ft) thick. All of the interior stones fit so well, a card won't fit between them. The sarcophagus is oriented in accordance with the compass directions, and is only about 1 cm smaller in dimensions than the chamber entrance. It might have been introduced as the structure was progressing.

New theories concerning the origin and purpose of the Pyramids of Giza have been proposed... Astronomic observatories... Places of cult worship... Geometric structures constructed by a long-gone civilization... Even extraterrestrial-related theories have been proposed with little evidence in support... The overwhelming scientific and historic evidence still supports the conclusion that, like many smaller pyramids in the region, the Great Pyramids were built by the great Ancient Egyptian civilization off the West bank of the Nile as tombs for their magnificent Kings... Tombs where Khufu, Khefre, and Menkaure could start their mystic journey to the afterlife.

The Hanging Gardens of Babylon

Fruits and flowers... Waterfalls... Gardens hanging from the palace terraces... Exotic animals... This is the picture of the Hanging Gardens of Babylon in most people's minds. It may be surprising to know that they might have never existed except in Greek poets and historians imagination!

On the east bank of the River Euphrates, about 50 km south of Baghdad, Iraq.

The Babylonian kingdom flourished under the rule of the famous King, Hammurabi (1792-1750 BC). It was not until the reign of Naboplashar (625-605 BC) of the Neo-Babylonian dynasty that the Mesopotamian civilization reached its ultimate glory. His son, Nebuchadnezzar II (604-562 BC) is credited for building the legendary Hanging Gardens. It is said that the Gardens were built by Nebuchadnezzar to please his wife or concubine who had been "brought up in Media and had a passion for mountain surroundings".

While the most descriptive accounts of the Gardens come from Greek historians such as Berossus and Diodorus Siculus, Babylonian records stay silent on the matter. Tablets from the time of Nebuchadnezzar do not have a single reference to the Hanging Gardens, although descriptions of his palace, the city of Babylon, and the walls are found. Even the historians who give detailed descriptions of the Hanging Gardens never saw them. Modern historians argue that when Alexander's soldiers reached the fertile land of Mesopotamia and saw Babylon, they were impressed. When they later returned to their rugged homeland, they had stories to tell about the amazing gardens and palm trees at Mesopotamia.. About the palace of Nebuchadnezzar.. About the Tower of Babel and the ziggurats. And it was the imagination of poets and ancient historians that blended all these elements together to produce one of the World Wonders.

It wasn't until the twentieth century that some of the mysteries surrounding the Hanging Gardens were revealed. Archaeologists are still struggling to gather enough evidence before reaching the final conclusions about the location of the Gardens, their irrigation system, and their true appearance.

Detailed descriptions of the Gardens come from ancient Greek sources, including the writings of Strabo and Philo of Byzantium. Here are some excerpts from their accounts:

"The Garden is quadrangular, and each side is four plethra long. It consists of arched vaults which are located on checkered cube-like foundations.. The ascent of the uppermost terrace-roofs is made by a stairway..."

"The Hanging Garden has plants cultivated above ground level, and the roots of the trees are embedded in an upper terrace rather than in the earth. The whole mass is supported on stone columns... Streams of water emerging from elevated sources flow down sloping channels... These waters irrigate the whole garden saturating the roots of plants and keeping the whole area moist. Hence the grass is permanently green and the leaves of trees grow firmly attached to supple branches... This is a work of art of royal luxury and its most striking feature is that the labor of cultivation is suspended above the heads of the spectators".

More recent archaeological excavations at the ancient city of Babylon in Iraq uncovered the foundation of the palace. Other findings include the Vaulted Building with thick walls and an irrigation well near the southern palace. A group of archaeologists surveyed the area of the southern palace and reconstructed the Vaulted Building as the Hanging Gardens. However, the Greek historian Strabo had stated that the gardens were situated by the River Euphrates. So others argue that the site is too far from the Euphrates to support the theory since the Vaulted Building is several hundreds of meters away. They reconstructed the site of the palace and located the Gardens in the area stretching from the River to the Palace. On the river banks, recently discovered massive walls 25 m thick may have been stepped to form terraces... the ones described in Greek references.

The Temple of Artemis at Ephesus

Is it simply a temple? How could it take its place among other unique structures such as the Pyramid, the Hanging Gardens, and the Colossus of Rhodes? For the people who actually visited it, the answer was simple. It was not just a temple... It was the most beautiful structure on earth... It was built in honor of the Greek goddess of hunting and wild nature. That was the Temple of Artemis (Diana) at Ephesus.

The ancient city of Ephesus near the modern town of Selcuk, about 50 km south of Izmir (Smyrna) in Turkey.

Although the foundation of the temple dates back to the seventh century BC, the structure that earned a spot in the list of Wonders was built around 550 BC. Referred to as the great marble temple, or temple D, it was sponsored by the Lydian king Croesus and was designed by the Greek architect Chersiphron. It was decorated with bronze statues sculpted by the most skilled artists of their time: Pheidias, Polycleitus, Kresilas, and Phradmon.

The temple served as both a marketplace and a religious institution. For years, the sanctuary was visited by merchants, tourists, artisans, and kings who paid homage to the goddess by sharing their profits with her. Recent archeological excavations at the site revealed gifts from pilgrims including statuettes of Artemis made of gold and ivory... earrings, bracelets, and necklaces... artifacts from as far as Persia and India.

On the night of 21 July 356 BC, a man named Herostratus burned the temple to ground in an attempt to immortalize his name. He did indeed. Strangely enough, Alexander the Great was born the same night. The Roman historian Plutarch later wrote that the goddess was "too busy taking care of the birth of Alexander to send help to her threatened temple". Over the next two decades, the temple was restored and is labeled "temple E" by archeologists. And when Alexander the Great conquered Asia Minor, he helped rebuild the destroyed temple.

When St Paul visited Ephesus to preach Christianity in the first century AD, he was confronted by the Artemis' cult who had no plans to abandon their goddess. And when the temple was again destroyed by the Goths in AD 262, the Ephesians vowed to rebuild. By the fourth century AD, most Ephesians had converted to Christianity and the temple lost its religious glamor. The final chapter came when in AD 401 the Temple of Artemis was torn down by St John Chrysostom. Ephesus was later deserted, and only in the late nineteenth century has the site been excavated. The digging revealed the temple's foundation and the road to the now swampy site. Attempts were recently made to rebuilt the temple, but only a few columns have been re-erected.

The foundation of the temple was rectangular in form, similar to most temples at the time. Unlike other sanctuaries, however, the building was made of marble, with a decorated façade overlooking a spacious courtyard. Marble steps surrounding the building platform led to the high terrace which was approximately 80 m (260 ft) by 130 m (430 ft) in plan. The columns were 20 m (60 ft) high with Ionic capitals and carved circular sides. There were 127 columns in total, aligned orthogonally over the whole platform area, except for the central cella or house of the goddess.

The temple housed many works of art, including four ancient bronze statues of Amazons sculpted by the finest artists at the time. When St Paul visited the city, the temple was adorned with golden pillars and silver statuettes, and was decorated with paintings. There is no evidence that a statue of the goddess herself was placed at the center of the sanctuary, but there is no reason not to believe so.

The early detailed descriptions of the temple helped archeologists reconstruct the building. Many reconstructions such as that by H.F. von Erlach depicted the façade with a four-column porch which never existed. More accurate reconstructions may give us an idea about the general layout of the temple. However, its true beauty lies in the architectural and artistic details which will forever remain unknown.

The Statue of Zeus at Olympia

This is the statue of the god in whose honor the Ancient Olympic games were held. It was located on the land that gave its very name to the Olympics. At the time of the games, wars stopped, and athletes came from Asia Minor, Syria, Egypt, and Sicily to celebrate the Olympics and to worship their king of gods: Zeus.

At the ancient town of Olympia, on the west coast of modern Greece, about 150 km west of Athens.

The ancient Greek calendar starts in 776 BC, for the Olympic games are believed to have started that year. The magnificent temple of Zeus was designed by the architect Libon and was built around 450 BC. Under the growing power of ancient Greece, the simple Doric-style temple seemed too mundane, and modifications were needed. The solution: A majestic statue. The Athenian sculptor Pheidias was assigned for the "sacred" task, reminiscent of Michelangelo's paintings at the Sistine Chapel.

For the years that followed, the temple attracted visitors and worshippers from all over the world. In the second century BC repairs were skillfully made to the aging statue. In the first century AD, the Roman emperor Caligula attempted to transport the statue to Rome. However, his attempt failed when the scaffolding built by Caligula's workmen collapsed. After the Olympic games were banned in AD 391 by the emperor Theodosius I as Pagan practices, the temple of Zeus was ordered closed.

Olympia was further struck by earthquakes, landslides and floods, and the temple was damaged by fire in the fifth century AD. Earlier, the statue had been transported by wealthy Greeks to a palace in Constantinople. There, it survived until it was destroyed by a severe fire in AD 462. Today nothing remains at the site of the old temple except rocks and debris, the foundation of the buildings, and fallen columns.

Pheidias began working on the statue around 440 BC. Years earlier, he had developed a technique to build enormous gold and ivory statues. This was done by erecting a wooden frame on which sheets of metal and ivory were placed to provide the outer covering. Pheidias' workshop in Olympia still exists, and is coincidentally -- or may be not -- identical in size and orientation to the temple of Zeus. There, he sculpted and carved the different pieces of the statue before they were assembled in the temple.

When the statue was completed, it barely fitted in the temple. Strabo wrote:

".. although the temple itself is very large, the sculptor is criticized for not having appreciated the correct proportions. He has shown Zeus seated, but with the head almost touching the ceiling, so that we have the impression that if Zeus moved to stand up he would unroof the temple."

Strabo was right, except that the sculptor is to be commended, not criticized. It is this size impression that made the statue so wonderful. It is the idea that the king of gods is capable of unroofing the temple if he stood up that fascinated poets and historians alike. The base of the statue was about 6.5 m (20 ft) wide and 1.0 meter (3 ft) high. The height of the statue itself was 13 m (40 ft), equivalent to a modern 4-story building.

The statue was so high that visitors described the throne more than Zeus body and features. The legs of the throne were decorated with sphinxes and winged figures of Victory. Greek gods and mythical figures also adorned the scene: Apollo, Artemis, and Niobe's children. The Greek Pausanias wrote:

On his head is a sculpted wreath of olive sprays. In his right hand he holds a figure of Victory made from ivory and gold... In his left hand, he holds a sceptre inlaid with every kind of metal, with an eagle perched on the sceptre. His sandals are made of gold, as is his robe. His garments are carved with animals and with lilies. The throne is decorated with gold, precious stones, ebony, and ivory.

The statue was occasionally decorated with gifts from kings and rulers. the most notable of these gifts was a woollen curtain "adorned with Assyrian woven patterns and Pheonician dye" which was dedicated by the Syrian king Antiochus IV.

Copies of the statue were made, including a large prototype at Cyrene (Libya). None of them, however, survived to the present day. Early reconstructions such as the one by von Erlach are now believed to be rather inaccurate. For us, we can only wonder about the true appearance of the statue -- the greatest work in Greek sculpture.

The Mausoleum at Halicarnassus

Similar to the Great Pyramid, we are now visiting the burial place of an ancient king. Yet the Mausoleum is different - so different from the Pyramid that it earned its reputation - and a spot within the list - for other reasons. Geographically, it is closer to the Temple of Artemis... And it was the beauty of the tomb rather than its size that fascinated its visitors for years.

In the city of Bodrum (f.k.a. Halicarnassus) on the Aegean Sea, in south-west Turkey.

When the Persians expanded their ancient kingdom to include Mesopotamia, Northern India, Syria, Egypt, and Asia Minor, the king could not control his vast empire without the help of local governors or rulers -- the Satraps. Like many other provinces, the kingdom of Caria in the western part of Asia Minor (Turkey) was so far from the Persian capital that it was practically autonomous. From 377 to 353 BC, king Mausollos of Caria reigned and moved his capital to Halicarnassus. Nothing is exciting about Maussollos life except the construction of his tomb. The project was conceived by his wife and sister Artemisia, and the construction might have started during the king's lifetime. The Mausoleum was completed around 350 BC, three years after Maussollos death, and one year after Artemisia's.

For 16 centuries, the Mausoleum remained in good condition until an earthquake caused some damage to the roof and colonnade. In the early fifteenth century, the Knights of St John of Malta invaded the region and built a massive crusader castle. When they decided to fortify it in 1494, they used the stones of the Mausoleum. By 1522, almost every block of the Mausoleum had been disassembled and used for construction.

Today, the massive castle still stands in Bodrum, and the polished stone and marble blocks of the Mausoleum can be spotted within the walls of the structure. Some of the sculptures survived and are today on display at the British Museum in London. These include fragment of statues and many slabs of the frieze showing the battle between the Greeks and the Amazons. At the site of the Mausoleum itself, only the foundation remains of the once magnificent Wonder.

The structure was rectangular in plan, with base dimensions of about 40 m (120 ft) by 30 m (100 ft). Overlying the foundation was a stepped podium which sides were decorated with statues. The burial chamber and the sarcophagus of white alabaster decorated with gold were located on the podium and surrounded by Ionic columns. The colonnade supported a pyramid roof which was in turn decorated with statues. A statue of a chariot pulled by four horses adorned the top of the tomb.

The total height of the Mausoleum was 45 m (140 ft). This is broken down into 20 m (60 ft) for the stepped podium, 12 m (38 ft) for the colonnade, 7 m (22 ft) for the pyramid, and 6 m (20 ft) for the chariot statue at the top.

The beauty of the Mausoleum is not only in the structure itself, but in the decorations and statues that adorned the outside at different levels on the podium and the roof. These were tens of life-size as well as under and over life-size free-standing statues of people, lions, horses, and other animals. The statues were carved by four Greek sculptors: Bryaxis, Leochares, Scopas, and Timotheus, each responsible for one side. Because the statues were of people and animals, the Mausoleum holds a special place in histroy as it was not dedicated to the gods of Ancient Greece.

Since the nineteenth century, archeological excavations have been undertaken at the Mausoleum site. These excavations together with detailed descriptions by ancient historians give us a fairly good idea about the shape and appearance of the Mausoleum. A modern reconstruction of the shorter side of the Mausoleum illustrates the lavish nature of the art and architecture of the building... a building for a King whose name is celebrated in all large tombs today -- mausoleums.

The Colossus of Rhodes

From its building to its destruction lies a time span of merely 56 years. Yet the colossus earned a place in the famous list of Wonders. "But even lying on the ground, it is a marvel", said Pliny the Elder. The Colossus of Rhodes was not only a gigantic statue. It was rather a symbol of unity of the people who inhabited that beautiful Mediterranean island -- Rhodes.

At the entrance of the harbor of the Mediterranean island of Rhodes in Greece.

Throughout most of its history, ancient Greece was comprised of city-states which had limited power beyond their boundary. On the small island of Rhodes were three of these: Ialysos, Kamiros, and Lindos. In 408 BC, the cities united to form one territory, with a unified capital, Rhodes. The city thrived commercially and had strong economic ties with their main ally, Ptolemy I Soter of Egypt. In 305 BC, the Antigonids of Macedonia who were also rivals of the Ptolemies, besieged Rhodes in an attempt to break the Rhodo-Egyptian alliance. They could never penetrate the city. When a peace agreement was reached in 304 BC, the Antagonids lifted the siege, leaving a wealth of military equipment behind. To celebrate their unity, the Rhodians sold the equipment and used the money to erect an enormous statue of their sun god, Helios.

The construction of the Colossus took 12 years and was finished in 282 BC. For years, the statue stood at the harbor entrance, until a strong earthquake hit Rhodes about 226 BC. The city was badly damaged, and the Colossus was broken at its weakest point -- the knee. The Rhodians received an immediate offer from Ptolemy III Eurgetes of Egypt to cover all restoration costs for the toppled monument. However, an oracle was consulted and forbade the re-erection. Ptolemy's offer was declined.

For almost a millennium, the statue laid broken in ruins. In AD 654, the Arabs invaded Rhodes. They disassembled the remains of the broken Colossus and sold them to a Jew from Syria. It is said that the fragments had to be transported to Syria on the backs of 900 camels.

Let us first clear a misconception about the appearance of the Colossus. It has long been believed that the Colossus stood in front of the Mandraki harbor, one of many in the city of Rhodes, straddling its entrance. Given the height of the statue and the width of the harbor mouth, this picture is rather impossible than improbable. Moreover, the fallen Colossus would have blocked the harbor entrance. Recent studies suggest that it was erected either on the eastern promontory of the Mandraki harbor, or even further inland. Anyway, it did never straddle the harbor entrance.

The project was commissioned by the Rhodian sculptor Chares of Lindos. To build the statue, his workers cast the outer bronze skin parts. The base was made of white marble, and the feet and ankle of the statue were first fixed. The structure was gradually erected as the bronze form was fortified with an iron and stone framework. To reach the higher parts, an earth ramp was built around the statue and was later removed. When the colossus was finished, it stood about 33 m (110 ft) high. And when it fell, "few people can make their arms meet round the thumb", wrote Pliny.

Although we do not know the true shape and appearance of the Colossus, modern reconstructions with the statue standing upright are more accurate than older drawings. Although it disappeared from existence, the ancient World Wonder inspired modern artists such as French sculptor Auguste Bartholdi best known by his famous work: The Statue of Liberty.

The Pharos of Alexandria

Of the Seven Wonders of the Ancient World, only one had a practical use in addition to its architectural elegance: The Lighthouse of Alexandria. For sailors, it ensured a safe return to the Great Harbor. For architects, it meant even more: it was the tallest building on Earth. And for scientists, it was the mysterious mirror that fascinated them most... The mirror's reflection could be seen more than 50 km (35 miles) off-shore.

On the ancient island of Pharos, now a promontory within the city of Alexandria in Egypt.

Shortly after the death of Alexander the Great, his commander Ptolemy Soter assumed power in Egypt. He had witnessed the founding of Alexandria, and established his capital there. Off of the city's coast lies a small island: Pharos. Its name, legend says, is a variation of Pharaoh's Island. The island was connected to the mainland by means of a dike - the Heptastadion - which gave the city a double harbor. And because of dangerous sailing conditions and flat coastline in the region, the construction of a lighthouse was necessary.

The project was conceived and initiated by Ptolemy Soter around 290 BC, but was completed after his death, during the reign of his son Ptolemy Philadelphus. Sostratus, a contemporary of Euclid, was the architect, but detailed calculations for the structure and its accessories were carried out at the Alexandria Library/Mouseion. The monument was dedicated to the Savior Gods: Ptolemy Soter (lit. savior) and his wife Berenice. For centuries, the Lighthouse of Alexandria (occasionally referred to as the Pharos Lighthouse) was used to mark the harbor, using fire at night and reflecting sun rays during the day. It was even shown on Roman coins, just as famous monuments are depicted on currency today.

When the Arabs conquered Egypt, they admired Alexandria and its wealth. The Lighthouse continues to be mentioned in their writings and travelers accounts. But the new rulers moved their capital to Cairo since they had no ties to the Mediterranean. When the mirror was brought down mistakenly, they did not restore it back into place. In AD 956, an earthquake shook Alexandria, and caused little damage to the Lighthouse. It was later in 1303 and in 1323 that two stronger earthquakes left a significant impression on the structure. When the famous Arab traveler Ibn Battuta visited Alexandria in 1349, he could not enter the ruinous monument or even climb to its doorway.

The final chapter in the history of the Lighthouse came in AD 1480 when the Egyptian Mamelouk Sultan, Qaitbay, decided to fortify Alexandria's defense. He built a medieval fort on the same spot where the Lighthouse once stood, using the fallen stone and marble.

Of the six vanished Wonders, the Lighthouse of Alexandria was the last to disappear. Therefore we have adequately accurate knowledge of its location and appearance. Ancient accounts such as those by Strabo and Pliny the Elder give us a brief description of the "tower" and the magnificent white marble cover. They tell us how the mysterious mirror could reflect the light tens of kilometers away. Legend says the mirror was also used to detect and burn enemy ships before they could reach the shore.

In 1166, an Arab traveler, Abou-Haggag Al-Andaloussi visited the Lighthouse. He documented a wealth of information and an gave accurate description of the structure which helped modern archeologists reconstruct the monument. It was composed of three stages: The lowest square, 55.9 m (183.4 ft) high with a cylindrical core; the middle octagonal with a side length of 18.30 m (60.0 ft) and a height of 27.45 m (90.1 ft); and the third circular 7.30 m (24.0 ft) high. The total height of the building including the foundation base was about 117 m (384 ft), equivalent to a 40-story modern building. The internal core was used as a shaft to lift the fuel needed for the fire. At the top stage, the mirror reflected sunlight during the day while fire was used during the night. In ancient times, a statue of Poseidon adorned the summit of the building.

Although the Lighthouse of Alexandria did not survive to the present day, it left its influence in various respects. From an architectural standpoint, the monument has been used as a model for many prototypes along the Mediterranean, as far away as Spain. And from a linguistic standpoint, it gave its name -- Pharos -- to all the lighthouses in the world... Just look up the dictionary for the French, Italian, or Spanish word for lighthouse.

The Seven Wonders of the Medieval Mind


Stonehenge is surely Britain's greatest national icon, symbolizing mystery, power and endurance. its original purpose is unclear to us, but some have speculated that it was a temple made for the worship of ancient earth deities. It has been called an astronomical observatory for marking significant events on the prehistoric calendar. Others claim that it was a sacred site for the burial of high-ranking citizens from the societies of long ago.

While we can't say with any degree of certainty what it was for, we can say that it wasn't constructed for any casual purpose. Only something very important to the ancients would have been worth the effort and investment that it took to construct Stonehenge.

The stones we see today represent Stonehenge in ruin. Many of the original stones have fallen or been removed by previous generations for home construction or road repair. There has been serious damage to some of the smaller bluestones resulting from close visitor contact (prohibited since 1978) and the prehistoric carvings on the larger sarsen stones show signs of significant wear.

Construction of the Henge In its day, the construction of Stonehenge was an impressive engineering feat, requiring commitment, time and vast amounts of manual labor. In its first phase, Stonehenge was a large earthwork; a bank and ditch arrangement called a henge, constructed approximately 5,000 years ago. It is believed that the ditch was dug with tools made from the antlers of red deer and, possibly, wood. The underlying chalk was loosened with picks and shoveled with the shoulderblades of cattle. It was then loaded into baskets and carried away. Modern experiments have shown that these tools were more than equal to the great task of earth digging and moving.

The Bluestones About 2,000 BC, the first stone circle (which is now the inner circle), comprised of small bluestones, was set up, but abandoned before completion. The stones used in that first circle are believed to be from the Prescelly Mountains, located roughly 240 miles away, at the southwestern tip of Wales. The bluestones weigh up to 4 tons each and about 80 stones were used, in all. Given the distance they had to travel, this presented quite a transportation problem.

Modern theories speculate that the stones were dragged by roller and sledge from the inland mountains to the headwaters of Milford Haven. There they were loaded onto rafts, barges or boats and sailed along the south coast of Wales, then up the Rivers Avon and Frome to a point near present-day Frome in Somerset. From this point, so the theory goes, the stones were hauled overland, again, to a place near Warminster in Wiltshire, approximately 6 miles away. From there, it's back into the pool for a slow float down the River Wylye to Salisbury, then up the Salisbury Avon to West Amesbury, leaving only a short 2 mile drag from West Amesbury to the Stonehenge site.

Construction of the Outer Ring The giant sarsen stones (which form the outer circle), weigh as much as 50 tons each. To transport them from the Marlborough Downs, roughly 20 miles to the north, is a problem of even greater magnitude than that of moving the bluestones. Most of the way, the going is relatively easy, but at the steepest part of the route, at Redhorn Hill, modern work studies estimate that at least 600 men would have been needed just to get each stone past this obstacle.

Once on site, a sarsen stone was prepared to accommodate stone lintels along its top surface. It was then dragged until the end was over the opening of the hole. Great levers were inserted under the stone and it was raised until gravity made it slide into the hole. At this point, the stone stood on about a 30° angle from the ground. Ropes were attached to the top and teams of men pulled from the other side to raise it into the full upright position. It was secured by filling the hole at its base with small, round packing stones. At this point, the lintels were lowered into place and secured vertically by mortice and tenon joints and horizontally by tongue and groove joints. Stonehenge was probably finally completed around 1500 BC.

Who Built Stonehenge? The question of who built Stonehenge is largely unanswered, even today. The monument's construction has been attributed to many ancient peoples throughout the years, but the most captivating and enduring attribution has been to the Druids. This erroneous connection was first made around 3 centuries ago by the antiquary, John Aubrey. Julius Caesar and other Roman writers told of a Celtic priesthood who flourished around the time of their first conquest (55 BC). By this time, though, the stones had been standing for 2,000 years, and were, perhaps, already in a ruined condition. Besides, the Druids worshipped in forest temples and had no need for stone structures.

The best guess seems to be that the Stonehenge site was begun by the people of the late Neolithic period (around 3000 BC) and carried forward by people from a new economy which was arising at this time. These "new" people, called Beaker Folk because of their use of pottery drinking vessels, began to use metal implements and to live in a more communal fashion than their ancestors. Some think that they may have been immigrants from the continent, but that contention is not supported by archaeological evidence. It is likely that they were indigenous people doing the same old things in new ways.

As Legend Has It The legend of King Arthur provides another story of the construction of Stonehenge. It is told by the twelfth century writer, Geoffrey of Monmouth, in his History of the Kings of Britain that Merlin brought the stones to the Salisbury Plain from Ireland. Sometime in the fifth century, there had been a massacre of 300 British noblemen by the treacherous Saxon leader, Hengest. Geoffrey tells us that the high king, Aurelius Ambrosius, wanted to create a fitting memorial to the slain men. Merlin suggested an expedition to Ireland for the purpose of transplanting the Giant's Ring stone circle to Britain. According to Geoffrey of Monmouth, the stones of the Giant's Ring were originally brought from Africa to Ireland by giants (who else but giants could handle the job?). The stones were located on "Mount Killaraus" and were used as a site for performing rituals and for healing. Led by King Uther and Merlin, the expedition arrived at the spot in Ireland. The Britons, none of whom were giants, apparently, were unsuccessful in their attempts to move the great stones. At this point, Merlin realized that only his magic arts would turn the trick. So, they were dismantled and shipped back to Britain where they were set up (see illus. at right) as they had been before, in a great circle, around the mass grave of the murdered noblemen. The story goes on to tell that Aurelius, Uther and Arthur's successor, Constantine were also buried there in their time*.

Present Day Stonehenge Situated in a vast plain, surrounded by hundreds of round barrows, or burial mounds, the Stonehenge site is truly impressive, and all the more so, the closer you approach. It is a place where much human effort was expended for a purpose we can only guess at. Some people see it as a place steeped in magic and mystery, some as a place where their imaginations of the past can be fired and others hold it to be a sacred place. But whatever viewpoint is brought to it and whatever its original purpose was, it should be treated as the ancients treated it, as a place of honor .

The modern age has not been altogether kind to Stonehenge, despite the lip service it pays to the preservation of heritage sites. There is a major highway running no more than 100 yards away from the stones, and a commercial circus has sprung up around it, complete with parking lots, gift shops and ice cream stands. The organization, English Heritage, is committed to righting these wrongs, and in the coming years, we may get to see Stonehenge in the setting for which it was originally created. Despite all its dilapidation and the encroachment of the modern world, Stonehenge, today, is an awe-inspiring sight, and no travel itinerary around Britain should omit it.

The Catacombs of Kom el Shoqafa

Alexandria, Egypt.

Alexandria, Egypt, represented a melding of cultures in the late first century A.D. Traditions of Greece and Rome overlay the city, the cult of Christianity was gaining ground, and memories of ancient Egypt's great kingdoms still lingered. It was a place where people seemed to have a talent for combining rather than destroying cultures.

Little of that "Paris of Antiquity" has survived above the ground. Below it, however, are haunting reminders of a culture that existed 1,900 years ago: the Catacombs of Kom el Shoqafa, "Mound of Shards." Carved out of solid rock, three levels burrow into the ground near the sites of the ancient stadium, and the long- vanished temple to Serapis, a Greek and Egyptian god. Many such catacombs once filigreed Alexandria's underground, but earthquakes and construction projects destroyed or obscured them. Only in 1900 was Kom el Shoqafa rediscovered after centuries - by a donkey that fell through a hole in the ground and into its access well. The animal, it soon became clear, had made an extraordinary archeological find.

An ancient circular staircase leads down into the catacombs. In the late second century, when Kom el Shaqafa was an active burial site, bodies were lowered by rope down the well formed by the spiraling stairs. The staircase ends at a landing vestibule, where two benches are carved into wall niches overarched by the cockleshell motif often found in classical designs.

A rotunda pierced by a six-pillared central shaft opens off the vestibule. To the left lies the triclinium, the funeral banquet hall where friends and family gathered on stone couches covered with cushions. Here they reclined while ceremonially feasting in memory of the deceased. Scholars believe that the catacombs at first may have served one family, but they were expanded into a mass burial site, probably administered by a corporation with dues-paying members. This theory could explain why so many chambers were hewn from the rock.

A staircase from the rotunda descends to the second level, an area eerily alive with sculpture. In the vestibule, two pillars are topped by the papyrus, lotus, and acanthus leaves of ancient Egypt, their frieze adorned by two falcons flanking a winged sun. Carved into wall niches are figures of a man, and a woman, perhaps the tomb's original occupants. The man's body assumes the stiff hieratic pose found in ancient Egyptian sculpture, but his head is in the lifelike manner of the classic Hellenes; the woman's stance is also rigid, but she sports a Roman hairstyle.

Three gigantic sarcophagi with lids that do not lift rest along the sides of the chamber. Scholars assume that bodies would have been inserted into them from behind, using a passageway that runs around the outside of the funeral chamber. Further circling this central tomb chamber is a hallway with 91 wall niches, each one providing burial space for three mummies.

Returning to the first level, visitors can reach a separate set of tombs through a breach in the rotunda wall, unintended by the original builders. It leads to what has been called the Hall of Caracalla, where bones of horses and humans were found. The hall's name comes from an episode in A.D. 215, when Emperor Caracalla ordered Alexandrian youths to review, then massacred them.

The Great Wall of China

The Great Wall started as earth works thrown up for protection by different States. The individual sections weren't connected until the Qin dynasty (221-206 B.C.). Qin Shihuangdi, First Emperor of Qin began conscripting peasants, enemies, and anyone else who wasn't tied to the land to go to work on the wall. He garrisoned armies at the Wall to stand guard over the workers as well as to defend the northern boundaries. The tradition lasted for centuries. Each dynasty added to the height, breadth, length, and elaborated the design mostly through forced labor.

It was during the Ming dynasty (1368-1644) that the Wall took on its present form. The brick and granite work was enlarged and sophisticated designs were added. The watch towers were redesigned and modern canon were mounted in strategic areas. The Portuguese had found a ready market for guns and canon in China, one of the few items of trade that China didn't already have in abundance. The Ming Emperors, having overthrown the Hun dominance and expelled their Mongol rulers of the North devoted large portions of available material and manpower to making sure that they didn't return.

Throughout the centuries, armies were garrisoned along the length of the Wall to provide early warning of invasion and a first line of defense. Great piles of straw and dung used to build signal fires have been found during excavations. There must have been small garrison towns spotted along the length. There weren't many farms or trade towns to provide ease, relaxation and food. The supply trails were over mountains along narrow paths. To bring supplies to the top, ropes were slung over posts set in the Chinese side of the wall and baskets were hauled up hand over hand. Supplies must have always been short and chancy, particularly in the winter.

The Wall served well. Only when a dynasty had weakened from within were invaders from the north able to advance and conquer. Both the Mongols (Yuan Dynasty, 1271-1368) and the Manchurians (Qing Dynasty,1644-1911) were able take power, not because of weakness in the Wall but because of weakness in the government and the poverty of the people. They took advantage of rebellion from within and stepped into the void of power without extended wars.

Over the past few centuries, the Great Wall has served as a source of building materials for local farms and villages. Aerial photos show that in sections, only the top battlements show -- the center of the wall has filled with sand and silt. The same brutal isolated conditions which made the Great Wall a triumph of engineering and determined planning make restoration problematic and slow.

The Porcelain Tower of Nanjing

Nanjing, China, out on the banks of the Yangtze.

The people of China called it Bao'ensi, the "Temple of Gratitude." European visitors who beheld the structure called it the Porcelain Tower of Nanjing and labeled it one of the wonders of the world. But warfare and subsequent destruction overtook it in the 19th century, and this remarkable structure was almost lost to history, virtually forgotten by the world.

Still, for many people who had known the tower firsthand, it was a sublimely elegant example of a Buddhist pagoda. "The best contrived and noblest structure of all the East," wrote Le Comte, the French mathematician who had made a visit to China in the early 19th century.

From an octagonal base about 97 feet in diameter, the tower's nine stories rose pyramidally to a height of about 260 feet. According to information obtained by an American missionary who journeyed to Nanjing in 1852, the original plan for the tower had called for 13 stories and a total height of about 330 feet. Although those ambitious dimensions were never realized, the smaller size made little difference, because size was not what made the structure so memorable for visitors.

The brilliant white porcelain bricks that faced the tower were what made it so unforgettable. By day, the bricks glittered in the sun, and at night they were illuminated by perhaps as many as 140 lamps hanging around the exterior of the pagoda. Worked into the porcelain panels were colorful stoneware tiles with green, yellow, white, and brown glazes forming images of animals, landscapes, flowers, and bamboo.

The Hagia Sophia

For centuries it stood at the heart of two of the world's great religions: To Christians it was Hagia Sophia, Church of the Holy Wisdom, mother church of the Orthodox faith and of the thousand-year-old Byzantine Empire. To Muslims, it became Ayasofya Camii, Mosque of Holy Wisdom and jewel of Istanbul. But to people of all faiths, it was, in the words of sixth-century historian Procopius, a "spectacle of marvellous beauty, overwhelming to those who know it by hearsay altogether incredible. For it soars to a height to match the sky...stands on high and looks down on the remainder of the city...."

In A.D. 326, Constantinople was laid out on the shores of the Bosporus by Emperor Constantine. Thirty years later, his successor built its first great church - eventually called Hagia Sophia - but it stood only 172 years before rioting crowds burned it to the ground. This event, in 532, was perhaps auspicious: It occurred during the reign of Justinian the Builder, who would give the world the sublime "tent of the heavens" that still stands and in whose creation "God has surely taken part."

Reconstruction started just 39 days after the destruction of the original church. The gigantic structure was modeled loosely on the Roman Pantheon. Measuring 220 feet by 250 feet along its main floor, it was laid out as a rectangle, at whose center was a square. Soaring 180 feet above the square was a dome supported by four massive pendentives on equally massive piers. At the east and west ends of the dome square were two have domes serving as the apse and entrance bay. The engineering feat was even more incredible considering that only brick, mortar, and stone were used. Although the earlier Romans knew how to make concrete, these Eastern builders did not.

Justinian embellished the interior with riches. Four acres of gold mosaics shimmered from the ceiling, and multicolored marble gleamed from the floors, columns, and wall panels.

Less than six years after work on it began, Justinian's monument to Christendom was completed. In A.D. 558 much of it collapsed due to the many earthquakes in the region. Because the initial architects, Anthemius and Isodorus, were no longer living, the latter's nephew, Isidorus the Younger, was given the task of rebuilding. This time it lasted 400 more years before collapsing again, and being again rebuilt.

In 1204, knoghts of the Fourth Crusade marched on the Byzantine Empire's capital city, stripping it and Hagia Sophia so remorselessly that a chronicler called it the most awesome plunder "since the creation of the world."

When Rome's hegemony ended 57 years later, the Church of the Holy Wisdom was devoid of glittering wealth. Bulky buttresses were built to shore it up, but its days of glory, and those of Constantinople, were drawing to a close. In 1453, Sultan Mohammed II massed the Ottoman army in front of the city. After a 53-day siege, the Byzantine Empire's great capital capitulated, and the conqueror marched into town and directly to Hagia Sophia. His ulama recited a Muslim prayer, and the sultan declared Eastern Christianity's cornerstone a mosque.

For almost 500 years it remained such, its mosaics whitewashed to hide the "idolatrous" figures of humans. Koranic inscriptions were placed in the four corners beneath the dome; four minarets were erected at the corners of the exterior perimeter; a gilded bronze crescent replaced the large metal cross crowning the basilica.

While the changes offended Christians, the Mosque of Holy Wisdom enjoyed a place of high regard among devotees of Islam. In the 20th century, Turkish leader Kemal Ataturk viewed the structure as a unifying symbol for East and West. He closed the mosque in 1932, uncovered its medeival mosaics, and reopened Hagia Sophia as a museum in 1934. Nearly 15 centuries after Justinian, it stands as a monument to both human and divine wisdom.

The Leaning Tower of Pisa

So this is the famous leaning tower of Pisa. When I first saw it I was impressed by its inclination. Looking around I realised that I was standing at one of the most beautiful squares in the world. This square is considered to be the most ambitious monument of the Tuscan Romanesque.

If you ever happen to be close to Pisa in winter or early spring you have to visit this square, the 'Piazza dei Miracoli' as they call it here. Go there early in the morning and taste this 'Miracolo'!

It's a pity that it's not possible anymore to climb the tower. It was closed some years ago because they feared that it could collapse. I never understood why there are problems in finding a solution for stabilizing the tower. Why don't they take the tower apart and reconstruct it again, but then on a solid foundation. Maybe even reconstructing it as the architect probably intented it to be.

The Seven Natural Wonders of the World

Mount Everest

Mount Everest is a rock and snow peak of the Himalayas. It is in Nepal and stands on the border of Tibet.

The expedition which first reached the summit, in 1953, was the eighth to make the attempt; there had also been three reconnaissance expeditions.
The peak was named after Sir George Everest. Its Tibetan name is Chomolungma.

Mount Everest is the highest mountain in the world. Its height is 29,028 ft. (8,848 m)

The Great Barrier Reef

Spanning more than 2000 km along the northeastern coast of Australia, the Great Barrier Reef is home to thousands of species of plants and animals. The Reef which runs parallel to the Queensland coast has been designated by the Australian Government as a Marine Park.

Few can imagine the biological diversity of the reef. One probably has to realize first that the 2000 km long reef runs predominantly in the North-South direction, therefore spanning a wide range of climates. Rain forests and mountains are predominant in the northern islands, while the southern islands are composed mainly of Coral Cay.

Apart from its environmental value, the area offers visitors a variety of activities including scuba diving, snorkeling, water sports, and birdwatching.

The Grand Canyon

The Grand Canyon of the Colorado River is the largest gorge in the world-a 290-mile-long gash across the face of the Colorado Plateau in northern Arizona. Rim to rim, it measures up to 18 miles across, with an average width of 10 miles; its average depth is one mile. Within this Delaware-size area of eroded rock rise mountains higher than any in the eastern United States and that dark walls of gorges millions of years old. Agent of this scene, the Colorado River drops 2,200 feet over nearly 200 rapids as it roars through the Canyon toward the Gulf of California.

Numbers, though, tell only part of the canyon's story and merely hint at the magic of its myriad hues, strata, spires, and gorges. The place is more than the sum of its parts-so much more that neither the eye nor the mind of the beholder can encompass more than a small part of it at one time. As John Wesley Powell, whose party in 1869 became the first to traverse the canyon by river, wrote, "You cannot see the Grand Canyon in one view, as if it were a changeless spectacle from which a curtain might be lifted. "

At the canyon's bottom, a mile below the rim, the Colorado River slices through Granite Gorge, exposing some of the oldest rocks visible anywhere on the earth. Nearly two billion years old, the Vishnu schist is the gleaming black remnant of a once towering mountain range. Some 500 million years after it formed, vast rifting and faulting laid it down the tilted, colorful sediments of the Grand Canyon Series atop schist. Ten distinct layers of sandstone, limestone, and shale bespeak the advance and retreat of ancient seas, the building up and wearing down of mountains, the meandering of rivers over 600 million years.

At either rim, visitors to date perch atop creamy Kaibab limestone cliffs studded with fossilized sponges, corals, snails, and shellfish that inhabited a warm inland sea 240 million years ago. Though rock layers once covered this ancient seabed, all geologic signs of the more recent Mesozoic and Cenozoic eras wore away eons ago.

Compared with the nearly two-billion-year process of deposition, erosion has set a brisk pace. The Grand Canyon itself is less than six million years old, created only since the Colorado River changed course and began flowing through the ancestral Colorado plateau. In just two million years, the river sliced to within 500 feet above its current depth. Wind, rain, snow, heat, and cold have helped the process along. So has the flow of hundreds of tributaries, many of which are dry washes, filled intermittently by snowmelt and summer thunderstorms. Over eons these streams have created " a composite of thousands, of tens of thousands, of gorges," as Powell marveled. "Every one of a world of beauty in itself."

The Grand Canyon is not only a slice of North America's geologic history but also a cross section of ecozones. Between rim and river, travelers find the same variety of ecological regions they would encounter on a trip from Canada to Mexico - from the snowy evergreen woods of the boreal zone to the arid depths of the lower Sonoran, where summer temperatures soar above 100oF and tenacious shrubs like creosote and ocotillo predominate. In all, the Grand Canyon provides rich and diverse habitat for more than 400 vertebrate species and 1,500 plants.

The human presence here stretches back at least 4,000 years, beginning with hunter-gatherers who deposited delicate split-willow animal figures in limestone caves. Before disappearing about A.D. 1150, ancient Pueblo peoples who had lived in and around the canyon for a millenium or more left a rich legacy of pottery, baskets, pictographs, and granaries and other structures in thousands of sites. The Havasupai people in the region today trace their presence back hundreds of years.

During the 20th century, humans have had a far more profound impact on the Grand Canyon than in all of the past. By 1900, the canyon was already a well-known destination, thanks to written accounts by explorers and scientists and to the glowing canvases of Thomas Moran. And after Grand Canyon National Park was established in 1919, the number of visitors continued to increase exponentially: About five million people now visit the canyon each year by car, on foot, atop mules, on motorized rafts, and in helicopters. Some of the human impact, such as the view-marring haze drifting in from power plants and urban centers, has been indirect. In 1963, the Glen Canyon Dam ended the Colorado River's free flow at the Grand Canyon's entrance, and that single action has changed the canyon more than any other event in human times.

To John Wesley Powell a century earlier, the sound of rushing water in the canyon was "a symphony of multitudinous melodies." But with the flick of a switch, the ebb and flood that had shaped the canyon's complex ecosystems over countless millenia were halted. Since 1963, the ecological richness of the canyon has sharply declined. In 1996, officials opened Glen Canyon Dam for a weeklong test flood designed to imitate natural flooding. While it failed to right the ecological imbalances that had taken hold, the event marked an important acknowledgement that nature's imperatives, though easily tampered with, have their own logic.

Victoria Falls

There are few appropriate superlatives that have not already been applied to this magnificent natural wonder of the world; in many ways it defies description. So vast are the Falls and their setting that it is difficult to grasp their true grandeur and for this reason, they are perhaps best seen from the air.

The Victoria Falls offer an inescapable closeness to the natural elements. The towering column of spray when the river is high, the thunder of the falling water, the terrifying abyss that separates Zimbabwe from Zambia, the forest - lined, placid, tranquil lagoons upstream in which hippo and deadly crocodiles lurk.

David Livingstone reported the existence of the Falls to the outside world in 1860. The result was immediate and from that point, the number of foreign visitors rose steadily. People walked, rode on horseback or traveled by ox - wagon from the Transvaal along what was then called the Hunters Road (now the border between Botswana and Zimbabwe) and on reaching George Westbeech's store at Pandamatenga left their animals there, safe from the lethal bite of the tsetse fly, and walked the remaining 80 kilometers, due north to the Falls.

With the conflict in South Africa finally resolved and the region politically more stable, tourism is developing rapidly. New activities are constantly emerging and the industry is becoming more and more sophisticated. Rafting the wild rapids below the Falls was the first innovation more than ten years ago.

Now the list of organized, commercial activities has expanded dramatically. Visitors can kayak, canoe, fish, go on guided walking safaris, ride on horseback, lunch on Livingstone's Island and in addition to the well-known "Flight of Angels", for the more adventurous there is micro lighting with stunning views of the Falls.

The Harbor of Rio de Janeiro

At the beginning of the 16th century, the Portuguese explorers who sailed down Brazil's coast kept tarck of their discoveries, and the days of the year, by naming the former for the latter. On New Year's Day, 1502, they glided toward a narrow opening in the coastline, guarded by fabulously shaped mountains. Beyond this entrance lay a body of water stretching 20 miles inland. Convinced that they had reached the mouth of a great river, they named the area River of the First of January.

The large waterway was not a river; it was an island-studded bay that the Tamoio people had long before named Guanabara - "arm of the sea." Nearly five centuries later, both the native and European names persist. But now, instead of caravels and dugouts, supertankers and yachts glide across the magnificent balloon-shaped harbor of Guanabara Bay. No longer a tropical wilderness teeming with tapirs and jaguars, the bay's western shores now hold a roaring metropolis called Rio de Janeiro - the River of January.

The great bay that looked like a river was only one of many illusions that Rio held. Europeans called the smaller bay of Botafago, under Sugarloaf, a "lake"; the Tamoio themselves named Guanabara Bay's eastern edge Niteroi, meaning "hidden waters." For early European voyagers, it was as though, when Rio hove into view, the curtain rose on a stage set with such strange, striking shapes and forms that virtually everything looked like something else.

Guarding the entrance to the bay, the naked and lopsided mountain the Portuguese called Pao de Acucar evoked the sugarloaves fashioned on the island of Madeira. They called the highest mountain Corcovado - "the hunchback" - for its humped profile. Today, a statue of Christ the Redeemer crowns the 2,300-foot-high peak.

The bay's vastness has been shrinking. With usable land at a premium, landfill has twice altered Guanabara Bay's contours. In the 1920s and again in the 1960s, small hills that once had been home to Rio's earliest settlers were sluiced through pipes to create bayfill. The new land now anchors an airport, a six-lane highway, parkland and beaches, the city's modern art museum, and other 20th-century landmarks as Rio looks to its great bay for elbow room.

Paricutin Volcano

On the afternoon of February 20, 1943, Dionisio Pulido, a farmer in the Mexican state of Michoacán, was readying his fields for spring sowing when the ground nearby opened in a fissure about 150 fee long. "I then felt a thunder," he recalled later, "the trees trembled, and is was then I saw how, in the hole, the ground swelled and raised it self 2 or 21/2 meters high, and a kind of smoke or fine dust–gray, like ashes–began to rise, with a hiss or whistle, loud and continuous; and there was a smell of sulphur. I then became greatly frightened and tried to help unyoke one of the ox teams."

Virtually under the farmer's feet, a volcano was being born. Pulido and the handful of other witnesses fled. By the next morning, when he returned, the cone had grown to a height of 30 feet and was "hurling out rocks with great violence." During the day, the come grew another 120 feet. That night, incandescent bombs blew more than 1,000 feet up into the darkness, and a slaglike mass of lava rolled over Pulido's cornfields.

The scientific world was almost as stunned as the hapless farmer himself by the volcano's sudden appearance. Around the world, volcanic eruptions are commonplace, but the birth of an entirely new volcano, marked by the arrival at the earth's surface of a distinct vent from the magma chamber, is genuinely rare. In North America, only two new volcanoes have appeared in historic times. One of them was western Mexico's Jorullo, born in 1759 some 50 miles southeast of Dionisio Pulido's property. The second, born about 183 years later in Pulido's field, was named Paricutín for a nearby village that it eventually destroyed.

Paricutín and Jorullo both rose in an area known for its volcanoes. Called the Mexican Volcanic Belt, the region stretches about 700 miles from east to west across southern Mexico. Geologists say that eruptive activity deposited a layer of volcanic rock some 6,000 feet thick, creating a high and fertile plateau. During summer months, the heights snag moisture-laden breezes from the Pacific Ocean; rich farmland, in turn, has made this belt the most populous region in Mexico.

Though the region already boasted three of the country's four largest cities–Mexico City, Puebla, and Guadalajara–the area around Paricutín, some 200 miles west of the capital, was still a peaceful backwater inhabited by Tarascan Indians in the early 1940s. Its gently rolling landscape, in a zone that had experienced almost no volcanic activity during historic times, was one of Mexico's loveliest. Although hundreds of extinct cinder cones rose around the small valleys, the only eruption in human memory had been that of distant Jorullo.

The Tarascan had no folk legends concerning volcanic eruptions in the area. But when Paricutín came into their lives, they saw events, in retrospect, that foretold the cataclysm. The first event was a sacrilege: the 1941 destruction of a large wooden cross on a hillside. The second one hinted at biblical retribution: a plague of locusts in 1942. When 1943 began, so did the third sign: a series of earthquakes; these were preceded, said one man, by "many noises in the center of the earth."

On February 19, the day before the volcano began to erupt, some 300 earthquakes shook the ground. On February 22, with the new cone rising and fiery skyrockets descending, the first of many geologists who would monitor and map Paricutín's behaviour over the next nine years arrived. From then on, Paricutín was under constant observation: It yielded a trove of information, including unique, fleeting glimpses of ephemeral features.

New volcanic phenomena and processes were sometimes obliterated almost as soon as they were recorded, especially during Paricutín's first year of violent, explosive growth and change. In that year, the cone topped 1,100 feet, four-fifths of its final height; explosions echoed all over the state of Michoacan; ash snowed on faraway Mexico City; and almost all of the vegetation for miles around the crater was destroyed.

During the summer of 1943, probably the volcano's most violent period. Lava rose to about 50 feet below the crater's rim. That fall, a new vent opened explosively at the cone's base, fountaining lava high into the sky. Lava finally destroyed the nearby villages the following year, but most villagers has seen their livelihoods disappear long before that.

Over the next years, lava flows continued with little interruption. But in February of 1952, almost exactly nine years after Paricutín was born, the volcano experienced its last major spasm of activity. By then, villages and farms had been relocated with government assistance. The new Bracero Program drew many of the displaced farmers to California for seasonal agricultural work.

The Northern Lights

Northern lights, or Aurora borealis brings together two mythological deities - Aurora, the Roman goddess of the dawn, and Boreas, Greek god of the north wind - to describe an event witnessed mostly at night in the high northerly latitudes. An identical phenomenon, the aurora australis, occurs in the high latitudes of the Southern Hemisphere, a region that has always been much more sparsely inhabited than the planet's northern reaches. Only a few eyewitness accounts of the aurora australis were available before 20th-century explorers arrived in Antarctica.

By contrast, the flowing ribbons, sky-filling swirls, otherworldly glow, gossamer veils, and brilliant rays of the aurora borealis are a regular presence that has awed and terrified northern peoples for thousands of years. To Finns the aurora was "fox fire" sparked by glistening fur. Some Alaskan Inuit saw the dancing souls of deer, seals, salmon, and beluga; others believed that if they whistled the lights might snatch them away. The Athabascan saw messages from their dead, the "sky dwellers."

For a long time, scientists offered almost as many interpretations of the northern lights as did the traditional peoples who observed them. The 20th century has brought with it studies of the earth's magnetism and the sun's workings. The aurora arises in the roiling turbulence of the sun. More than 100,000 times hotter than boiling water, the sun's interior chops the atoms that form solar gases into a thin stream of electrically charged particles - protons and electrons. Both matter and energy, this stream continuously erupts from the sun and is called the solar wind. Two or three days after bursting from the sun's surface at speeds of up to 500 miles a second, the solar wind reaches the earth, 93 million miles away.

The solar wind has the force to swiftly annihilate life on earth. What stops it from doing so is the shielding power of the planet's magnetic field, reaching out more than 40,000 miles into space. Like the earth, the sun is also a mighty magnet, and the solar wind carries fragments of its magnetic field. As solar particles crash into the planet's magnetic field, the fields repel each other.

Though most of the solar wind harmlessly sideswipes the magnetic shield, small streams of solar particles do manage to become trapped, spiraling down toward the planet's north and south magnetic poles. As they tumble, beams of electrons spread, ripple, and swirl, and yet their movements remain invisible. But when the solar wind hits the upper reaches of the ionosphere and encounters atmospheric gases, it starts churning the thin soup of oxygen and nitrogen there. Marvelous shapes and flowing patterns begin to appear. Electrons bouncing around among atoms of oxygen create a greenish glow much lower. Nitrogen molecules hit by solar wind may shine bright pink, or blue and violet, depending upon their distance from the surface.

The ever changing dance of lights belies the aurora's permanence. Though only parts of it can be seen at any time, and almost never during the day, the aurora borealis forms a 2,000-mile-wide auroral oval above the magnetic north pole day in and day out, year after year.

What can dramatically change the oval are the occasional spikes in solar activity that turn the solar wind into a raging hurricane. Then, for a few days, the auroral oval flows toward the Equator and treats sky-gazers as far south as Mexico to midnight extravanganzas. At the same time, electromagnetic disturbances intensify, with overloaded power lines and scrambled communications serving to remind us of the force behind the celestial fireworks.

The Seven Underwater Wonders of the World


The warm waters of Palau, a small archipelago in the Pacific Ocean, hold perhaps the richest and most biologically diverse coral reefs on the planet. In this "cradle of diversity," marine biologists have recorded 700 species of corals and 1,500 species of fish.

Palau's coral reefs began to grow millions of years ago when coral polyps colonized submerged volcanic mountains. The tiny polyps produced a material that cemented them in place. Side by side, they built hard, external skeletons around their soft bodies, and when they died, other corals built skeletons on top of them. Geologic forces eventually raised the coral topped mountains above the sea, and all the exposed corals died. In time, new colonies built more reefs on the islands undersea slopes.

Today, divers swimming over the coral gardens of Ngemelis Island are moved by nature's artistry and creativity. The top of this reef, just a few feet below the surface, resembles wild flowers swaying in the breeze. Here, soft coral trees and bushes seem to have been painted in stunning shades of green, red, yellow, and orange.

Among the many fish species fluttering around gracefully are yellow butterflyfish, blue-headed wrasses, and emperor angelfish-black masked and striped. Not so graceful, though, is the mango-size puffer, a fish that sucks in water when startled and inflates its body to the size of a football. Sharp spikes stick out in all directions and are quite a deterrent to potential predators. Another cumbersome swimmer is the pear-sized trunkfish, whose tough, trunklike body is difficult for predators to chew.

Nestled among the Ngemelis corals are giant clams. These two- or three-foot-long creatures, depicted in early movies as being able to grab divers' feet, feed harmlessly on plankton-not divers. And poking ever so slightly out of cracks in the corals are green and red brittle stars. Related to sea stars, these animals grow arms that break off easily if bitten by predators or touched by scuba divers. Brittle stars hide until sundown, but at night they crawl out, spread their arms, and feed on plankton.

Sometimes the best way to observe fish is to find a sandy patch, settle down, and wait, letting them get accustomed to you. And a good technique for finding a particular kind of fish is to look from right to left, rather than left to right-the usual way in which people view things. Looking in this manner slows down the viewing process and increases the odds of sighting an animal.

Not difficult to spot are watermelon-size cuttlefish hovering in the water. Related to the octopus and squid, these members of the cephalopod group can change their colors, patterns, and shapes so that they sometimes look like floating plants or free-swimming octopuses, their arms tickling unseen objects. Another master at deception is the crocodilefish. A lie-in-wait predator, this three-foot-long fish has an uncanny resemblance to its reptilian namesake.

One of the greatest underwater shows on earth can be seen at Blue Corner, a part of the archipelago named for the deep blue quality of its water. Here, currents strong enough to rip the mask from a diver's face bring in a healthy supply of plankton, a food source that attracts unicornfish, tangs, and other plankton-eaters. In turn, these fish attract huge schools of predators, including sharks and jacks. The school of jacks can number 300 or 400 and be so dense that it nearly blocks the sunlight, creating the effect of an underwater eclipse. Blue Corner also attracts manta rays and eagle rays. With wingspans of several feet, these large plankton-feeders have few predators and can feed leisurely without having to worry about the ever present sharks patrolling the reef.

At Blue Corner, the currents are so fast that a diver's encounter with a pelagic fish may last only a few minutes before he or she is whisked into the open ocean. Some divers overcome the time constraints of current diving by using a reef hook, a three-foot-long line with a hook at both ends. One hook attaches to a scuba vest and the other to a nook or cranny in the reef. The hook extends the dive, but in the process of setting, adjusting, and releasing it, a diver damages the fragile corals. Healthy coral gardens are found in many other areas of Palau, but at Blue Corner major areas of coral are now barren white patches of rock. This little corner of the world shows what can happen when underwater wonders are overwhelmed by people's desire to see them at any cost.

Among Palau's other attractions are 80 marine lakes. Jellyfish lake, with its extraordinary jellyfish population, is the most visited. Like the others, it is dark green, has poor visibility, and is as warm as bathwater. Each day, jellyfish slowly follow the sun's path across the lake, soaking up sunlight for the life-supporting algae in their tissues. Because they haven't needed to protect themselves from predators, these jellyfish have lost the ability to sting. Their lake was sealed off from the open ocean eons ago, and jellyfish-eaters, such as turtles, were locked out. Without the threat of getting stung, today's underwater explorers can swim freely among yellow polka-dotted jellyfish shimmering harmlessly in the sun.

The Belize Barrier Reef

The second largest barrier reef in the world rises from the seafloor off the coast of Belize. A diver's paradise, it is known for fascinating coral formations, myriad fish and invertebrates, and exceptional water clarity.

On the ocean side of this 160-mile-long reef is a popular tourist designation known as Lighthouse Reef. Here, crystal-clear waters fill the famous Blue Hole, a crater more than 1,000 feet across and just over 400 feet deep. At the surface, healthy coral formations rim this wonder within a wonder, but at a depth of 125 feet, neither corals nor fish can be found. Instead, a diver finds stalactites formed during the Ice Age, when the world sea level was much lower and the Blue Hole was a subterranean cavern. The hole formed when the cavern's roof collapsed.

To the south is Glover's Reef, surrounded by waters so clear that visibility even at night is quite good: The long shaft of a diver's torch can pierce the water to a distance of 15 feet. Because it is several miles from the mainland, this reef is not affected by silt and sediment runoff. At Glover's, the arrival of a diver startles bright red cardinalfish swimming in open water, they rely on organs called lateral lines running along both sides of their bodies. A combination of sonar and radar, a lateral line senses vibrations and movements in the water, allowing fish to detect predators and pray. It's also an early warning device. As a fish swims, it creates a sort of bow wake that bounces off solid objects. When another fish feels the wake, it moves to avoid a collision.

Glover's Reef is home to the Emerald Forest, a site named for magnificent elk horn coral "trees" having trunks a foot diameter and canopies more than ten feet high. Several kinds of exotic fish also live here, and at night, a camera-bearing diver can catch them asleep, tucked in against the reef, but still out in the open. Butterflyfish as colourful as backyard butterflies hover in the water. So do hogfish with pig like snouts, trumpetfish that look like two-foot-long musical instruments, and parrotfish, their beaklike mouths closed for the night.

Not all of the reef's creatures are lost in sleep, however. Manta rays and sharks prowl the darkness, seeking meals. Lobsters, crabs, shrimp, and nudibranchs (the beautiful slugs of the sea) search the reef for food and mates. A Nassau grouper gets its mouth "cleaned" by a tiny shrimp, which darts from side to side and from top to bottom to remove small parasites and dead flesh from the cooperative fish, its mouth frozen in a wide yawn. The shrimp gets a free meal, so to speak. Dr. Mary Wicksten, a marine biologist at Texas A&M University and a specialist in these so-called cleaning stations, says that fish seek out established stations on the reef because the activity is important for their health. Like several other reef fish, the Nassau grouper is remarkable for its ability to change sex as it gets older, increasing its chances for reproductive success when another grouper is met.

At a natural cut in Glover's Reef, where water surges during the changing of the tide, a diver can free-fall horizontally, whipped along by the strong current. But fish hover without obvious effort, their streamlined bodies designed by nature to keep them in place in such conditions. Jutting from the walls of the cut, like fingers on a huge hand, are lavender tube sponges that eat by filtering tiny plants and animals from the sea. Soft coral sea fans, also filter feeders, bend in the breeze like underwater current that brings them a constant supply of food. The dominant life-form here is the hard coral, which is capable of withstanding the force of very strong wave action.

Where the current exits this canyon, it stirs up sand from the floor of a lagoon, reducing visibility. Somewhere near the bottom, turtles and manatees leisurely feed on sea grasses, while small coral heads form mini-reefs alive with tiny fish.

Across the lagoon is the Hol Chan Marine Reserve, a small area off Ambergris Cay where the tangled roots of a mangrove forest reach into the water. Even here, small fish dart among the roots, looking for meals or protection from predators.

Hol Chan, which is Maya for "the cut," was established in 1987. It encompasses all three habitats of the barrier reef ecosystem: reef, lagoon, and mangroves. Although separate, each area depends on the others. Marine scientist Jacque Carter, who has long studied Belize's fish, writes: "The mangroves are a feeding and breeding ground for reef fishes; they also trap silt and sediment runoff before it reaches the reef. The lagoon is...a feeding ground for many reef fishes, and the sea grasses...trap reef-smothering particles [keeping them] from reaching the lagoon, mangroves and shore areas from destructive wave action. If one area is damaged, the others are also affected – which is why it is important to protect the entire system, and not just the beautiful coral reef."

The Galapagos Islands

Rising from the Pacific 600 miles west of Ecuador are arid islands whose name, for obvious reasons, is a Spanish word for tortoises. Indeed, the Galapagos islands are famous for tortoises weighing hundreds of pounds. What many people don't know, though, is that fascinating creatures also live in an undersea realm offshore.

Describing the contrast between the islands and their underwater bounty in a the 1924 book of, Galapagos: World's End, William Beebe wrote: "Host of sally-lightfoots [tidal crabs] were the most brilliant spots of color above the water in the islands, putting to shame the dull, drab hues of the terrestrial organisms and hinting at the glories of colorful animal life beneath the surface of the sea. "

Four currents converge in Galapagos waters: the Peru or Humboldt to from the south, the Equatorial from the West, the North Equatorial, and the Panama. Fish and invertebrates from different oceans and habitat ride these currents and quickly make themselves at home along the rocky shores, on a sandy sea bottom, and in the mangrove forests of the Galapagos.

Among the most playful creatures here are the sea lions. Slicing through the water at dazzling speed, they sometimes perform an underwater ballet of sorts, twisting, turning, stretching, and arching their sleek bodies amid clouds of plankton. A sea lion will swim just inches from a diver's mask as if approaching for a kiss, or it will nibble at a swim fin or embrace the diver with its flippers, all the while maintaining eye contact-a technique that requires incredible flexibility and agility.

A sea monster the size of a school bus also lives in Galapagos waters: the whale shark. Largest fish in the sea, it eats plankton and fish strained from the water by its wide mouth. Although encounters with it are rare here, encounters with other sharks are not. Six- to eight-foot-long hammerhead sharks, with heads shaped like sledgea hammers, swim in schools of a hundred or more. White-tip, Galapagos, and bull sharks, most larger than a man, are seen by nearly every explorer who enters these waters. Getting pictures of them while diving is difficult, though, because a diver's bubbles seem to frighten them.

Among the more unlikely denizens of equatorial waters are Galapagos Penguins. Only here and along the Pacific coast of South America do Penguins live near the Equator. They ply these waters with great ease, chasing fish and avoiding sharks. Out of water, they may be seen waddling about on the islands' volcanic rocks.

Another unique animal is the marine iguana, a ferret-size lizard whose distinctly reptilian features are adaptations for its life in the Galapagos: it uses its blunt snout to scrape algae from submerged rocks, it's clawed feet to grip slippery rocks, its muscular body and tail to swim in strong tides, and its spines to defend against predators.

Although the archipelago holds many wonders, it does not have a coral reef. Instead, diver's find dramatic volcanic rock formations beneath the sea. Some of them are bare; others are covered by red algae, orange and costing sponges, orange cup corals, and bushes of black coral.

One reason for the low number of reef-building corals is a weather phenomenon called El Nino. Periodically, El Nino brings an incursion of water that is poor in nutrients and unusually warm; these conditions are unfavorable for corals and plankton. El Nino also causes rainfall to increase, and large amounts of freshwater added to seawater are detrimental to coral growth.

Conversely, these seas hold a high number of fish-300 species, of which 17 percent are endemic. Among them are the hieroglyphic hawkfish, a bottom-dweller that seems to have symbols etched on its body, and the red-lipped batfish, with fashion-model-red lips. Not surprisingly, the archipelago attracts many fishermen.

Although the area is protected by an 1986 presidential decree making it the Marine Resource Reserve, it is still the site of illegal fishing. Park rangers simply don't have the resources to patrol almost 30,000 square miles. Luckily, the conservation effort is strong, being led in part by the owner of live-aboard dive vessels, Herbert Frei, Jr., who says that a plan is in the works to provide fisherman with a livelihood, while not significantly affecting the underwater habitat.

Efforts are also under way to save the islands' terrestrial animals, especially the tortoises. Because their shells come in different sizes and shapes-domed, saddle-back, or somewhere in between-these gentle giants formerly were thought to be members of several species. In fact, there is only one species, and it was almost wiped out by hunting and habitat destruction. Today, scientists at the Charles Darwin Research Station are working to protect and, in some cases, reintroduce the giant tortoises to more remote areas of the archipelago.

Fortunately some 750,000 birds still can be found among the islands. Flycatchers, mockingbirds, yellow warblers, hawks, owls, and finches are common. So far 19 species of seabirds, including the blue-footed booby, red-footed booby, frigate bird, and the waved albatross.

When naturalized Charles Darwin first came to the Galapagos in 1835, he noticed that animals of the same species looked different on different islands. Years later, he developed a revolutionary theory of evolution and wrote On the Origin of Species by Means of Natural Selection. What might he have thought if he had also seen the remarkable creatures in the sea surrounding islands?

The Northern Red Sea

Surrounded by one of the world's largest expanses of sand, the Red Sea laps the shores of an ecosystem seemingly devoid of life. For that reason, many people find it difficult to imagine that some of the earth's richest coral reefs rise from the floor of the sea's northern reaches.

Marine scientist Eugenie Clark has no such difficulty: "If I could only dive in one place in the world, I would choose Ras Muhammad. " Having researched life in the Red Sea for more than four decades, she believes that this area best represents the Red Sea's many marine splendours. In 1980, Dr. Clark encouraged the Egyptian government to make the site a national park, an idea that became a reality in 1983.

A coral plateau in deep water, Râs Muhammad has sometimes been called an underwater Garden of Eden, a quiet place with the feel of a church. Shafts of sunlight illuminate the the reef's, yellow, orange, and light green soft corals. hard corals such as stars, fingers, and clubs are also found here, ensuring that the community is rock solid.

Some sea anemones on the reef seem to glow a brilliant shade of orange, a color that comes from algae in their tentacles. Although many photographers have tried, no one has yet been able to capture this glove on film. Now and then a diver will witness a very rare sight: bright-red lionfish swimming in open water during the day. Equipped with the venemous dorsal spines, these fish usually reside near the sea bottom, waiting to trap smaller fish in nooks and crannies.

Several divers have met "George," a reef monster the size of a beanbag chair. A humphead wrasse, this fish has chameleon eyes, cowlike lips, and a body pattern in the form of an intricate green maze on a blue background. Although George is a strange-looking creature, he is, in fact, a friendly fish seeking only hand outs from divers.

At Râs Muhammad some divers also have unforgettable encounters with the reef triggerfish. One moment this foot-long fish may be blowing water into a small hole on shallow ledge. The next instant it may be charging at full speed, its fangs bared. But two feet away, it will suddenly stop, like a flying saucer in a science fiction movie, and retreat. The triggerfish repeats this charge several times. When it no longer feels threatened, it goes about its business, perhaps tending its nest of newly laid eggs.

Another popular reef, Anemone city, boasts vast numbers of anemones. This reef is a swaying shag carpet of white and green tentacles. Darting in and out among tentacles are hundreds of clown fish, sporting upside down smiles, and a domino-fish, their black bodies dotted with white spots.

For the sport diver, Anemone city provides a great great deal of entertainment. But for marine scientists and divers who are interested in the mysteries of the sea, it is a living laboratory and a stage for observing one of the most fascinating examples of symbiosis in the marine world-the relationship between clownfish and sea anemones. A clownfish, for its part, protects an anemone not from fish that like to eat its soft tentacles. The anemone, in turn, offers a haven for the clownfish, which find safety among tentacles whose stings, for some reason, don't hurt it.

Clownfish present marine scientists with another interesting aspect of life in the sea. These fish, like many other reef fish species, are hermaphrodites: they have both male and female sex organs, although not at the same time. Such attributes increase the chance of a species' survival. If a female clownfish is eaten or dies naturally, for example, the largest juvenile turns into a breeding female.

Adventurous divers can explore caves and caverns at the site known as Fishermen's Bank. Here in the darkness, large schools of hatchet-shaped glassy sweepers swim in tight formation, fluttering their tiny fins and making swishing sounds as they sweep around divers bodies. Lionfish may swim near the ceilings of the caves, their venemous dorsal spines pointing downward toward divers' heads. In some caves, small openings in the ceilings are penetrated by dramatic shafts of light, an underwater show that frequently mesmerizes divers bold enough to swim here.

To learn why the Red Sea has such a diversity of species-one thousand species of tropical fish and four hundred species of corals-scientists have had to go a long way back in time. 30 million years ago, the Red Sea was closed at its southern end. Its northern end, however, opened into the Mediterranean Sea, allowing Atlantic species to enter and breed. About 10 million years later, shifts in the earth's tectonic plates closed the Red Sea's northern end and opened its southern one, letting in species from the Indian Ocean. The tectonic shifts had produced a sea with both Atlantic and Indo-Pacific species, although the latter now dominate.

Another reason for the diversity of marine life is the region's exceptionally clear skies. Intense sunlight provides abundant solar energy for the corals and the photo-synthesizing zooxanthellae that live inside them. The more sunlight corals get, the faster they grow. Healthy reef structures in the Red Sea have more places for fish to find food and hide from predators; hence, a healthier, more diverse fish population that is a wonder to behold.

Lake Baikal

In early March, snow still blankets lake Baikal, its deep waters sealed beneath three-foot-thick ice. Over the next two months, under bright springtime sun, the ice will slowly thaw in a process punctuated by cracking sounds not unlike the sharp report of guns. As long as the ice remains in place, though, scientists can set up camp right in middle of this 400-mile-long, 5,000-foot-deep lake.

Russia says "Sacred lake" is 25 million years old-the oldest lake on the planet. It is also the deepest lake, holding more water than all of North America's Great Lakes combined. It's aquatic life comprises more than 1,500 animal species and 1,000 plant species, two-thirds of which are endemic. According to marine scientist Andy Rechnitzer, Baikal is more biologically diverse than other lakes because oxygen-rich water circulates from its surface to its deepest depths, a process likely related to geothermal vents.

One of the most interesting animals in the lake is the Baikal seal, or nurpa, the world's only fresh water seal. Nurpas use their sharp claws to carve dens for their families while ice is still forming. Finding their dens is relatively easy: look for air bubbles trapped in the ice after being exhaled by nurpas. You can also look for small breathing holes poked into snowdrifts by the seals.

For a diver to get into a den is another story. First, a diving crew member must use a small metal saw to cut a small hole in the ice. Then a circular, manhole-size opening is cut with a chain saw, and long poles are used to push the round slab under the ice. To keep the hole from freezing over, it must be constantly raked. A team effort, indeed. Under the ice, the water is warmer than the air [36 degrees F], but it is still very cold for scuba diving. Every 30 seconds or so, divers must tug on safety lines attached to their wrists to let the crew above know that they are all right.

Seen from an underwater perspective, the seal's den is an intricate ice carving, complete with tunnels and an igloo-like canopy that functions as an air pocket. Nurpas are shy, and pups resting on a bunk bed of ice quickly dive into the water when startled by a visitor.

In June, conditions at Lake Baikal are much different. Although the water temperature is about the same as it is in spring, the air temperature is usually in the 60s. Visibility underwater is perhaps 200 feet, many times greater than that in most lakes. The "Great vis" at that time of year is caused by the water's relative lack of minerals and by countless small crustaceans eating the algae, plankton, and bacteria that can cloud fresh water and salt water alike. Clarity does not last long, however. By mid July, an algae bloom produces pea-soup conditions.

Except for the numbing cold that pains their ears, face, and fingers within minutes of entering the water, divers exploring the shallows of Baikal might feel as if they are hovering over a meadow on a sunny day. Looking up from a depth of 50 feet, they can see clouds in the sky. Looking down, they sea fields of fluffy green algae.

The greens spires of three-foot-tall candelabra sponges poke through the algae. Such large sponges, which get their color from algae living symbiotically in their tissues, are not rare in saltwater, but in other freshwater lakes they have no parallel. The sponges are homes for amphipods, alien-looking shrimplike creatures that are as small as specks or as large as human thumbs. And the waters of Lake Baikal hold 240 species of them.

Hiding among the sponges and algae are sculpins, bottom-dwelling fish that are masters of camouflage, their patterned bodies blending in with their surroundings. These ancient fish, like most cold-water species, don't move fast; it's just too cold here to make quick moves. So, the lake's 40 species of sculpins, comprising 80 percent of Baikal's fish biomass, rely on camouflage for protection against larger fish. Pear

Near the lakes northern and, at a depth of approximately 1,350 feet, a geothermal vent provides warmth for the community of sponges, snails, worms, and fish living in the pitch-dark environment. The existence of this vent confirms that Baikal is a place where continental masses are being pulled apart. Photographer Emory Kristof, who has visited the site for the National Geographic Society, explains: "The communities of life resemble organisms normally found in an ocean, which gives weight to the theory that Baikal is an ocean in the making."

One rarely seen creature is the omul, a delicious fish endemic to the lake. Its scarcity indicates Baikal is ecologically out of balance, a result of the destructive effects of industrial development and logging nearby. Vadim Fialkov, of the lake Baikal Limnological Institute, reports that "local environmental groups have put pressure on the government to reduce the amount of effluents that are dumped into the lake. With some luck, we'll get Baikal back to its pristine state and keep it that way. "To help the effort, UNESCO has recommended that the lake and its watershed be designated a World Heritage Site."

The Great Barrier Reef

Already explained for this site

The Deep Sea Vents

In the blackness of night, on a remote part of the planet, a volcano erupts. Thick plumes of what looks like black smoke billow from it. Escaping magma blankets the terrain; temperatures soar to more than 600o F. deep cracks formed around the volcano, and superheated water seeps from them.

Local residents do not evacuate the area. While the magma is fatal to them, the hot water is not, and thousands are able to thrive in a seemingly hellish habitat.

The violent eruption, which has been going on for weeks, is not typical volcanic activity. It is happening at a deep-sea vent more than 8,000 feet below the surface of the ocean.

Deep-sea vents are also known as deepwater seeps, deep-sea springs, and hydro-thermal vents. Found at the bottom of the ocean, they are created by volcanic and tectonic activity in areas where huge hostile plates are converging or spreading apart. Magma erupts along the margins of these plates, usually slowly, but sometimes with such ferocity that it creates instant lava lakes. The thick black smoke is actually a plume of metal-rich, superheated water billowing out of the silt- and sediment-covered, gray-and-black chimney-an underwater volcano. Hope

Under thousands of pounds of pressure per square inch, sea water gradually seeps into the vents, where it is superheated and filled with manganese and other minerals before it is eventually returned to the ocean. This discovery has led some scientists to speculate that each drop of sea water circulates through the earth's crust, by way of the vents, every 10 to 20 million years. Before the discovery of the vents, most scientists thought that all of the minerals in the sea were dropped into the ocean by continental rivers.

Because no sunlight reaches the depths where the vents are found, these underwater wonders are visible only in the floodlights of a manned submersible such as Alvin. This three-person submarine, which can descend 12,800 feet below sea level, first took photographs and research scientists to see vents along the Galapagos rift in 1977, when the original discovery was made.

The residents of the vent community, although surely not the prettiest creatures, are perhaps the most fascinating of all the world's underwater wonders from a scientific perspective. At the geothermal vents, marine biologists have an opportunity to study a food chain that functions without sunlight. Most biologists had once believed that only sunlight, through photosynthesis, could support life on Earth. At the vents, however, life begins with bacteria that metabolize hydrogen sulfide. The bacteria, in turn, become food for the other animals in the vent community.

Among the 300 species of life found near the vents, perhaps the best documented life forms are the giant red-tipped tube worms-12-foot-tall creatures whose 300,000 tentacles strain food from the water. By comparison, tube worms in shallow ocean have a dozen or so tentacles and grow only a few inches long.

Blind crabs and shrimp, which don't need to see in a lightless world, live among octopuses that eat crabs and mussels. Equally fascinating residents include pink ventfish, sea cucumbers, sponges, and brittle stars, flowerlike animals that use their fine appendages to anchor themselves to rocks.

Mussels are among the 48 documented species of mollusks found in vent communities. And some specimens of giant clams that live in this environment measure almost ten inches in length.

How does a vent become colonized? Some species, while in their larval stage, travel tremendous distances through a virtually lifeless and totally lightless realm to colonize and new vent on the seafloor. But other species first travel to the surface to feed before settling down at a new deep-sea vent.

Several of these vents have been found and explored in both the Pacific and the Atlantic, while others likely remain hidden a mile or more below the sea surface and await discovery. Scientists who study the life-forms near the vents believe that the bacteria there, as insignificant as they may seem to most people, may provide clues to how life first formed on this planet so many millions of years ago.

The Seven Wonders of the Modern World

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