But every bit as fascinating are the stories of once-great civilizations forced to submit to nature's capricious power. Ancient ruins in Pompeii face ruin againHere are seven ancient cities -- almost all UNESCO World Heritage sites -- that tell of triumph and failure in the face of dramatic conditions. Perhaps they also offer a cautionary tale for the modern world: No matter how advanced the civilization, we are often no match for nature.Pompeii, ItalySixteen years before Mount Vesuvius enveloped Pompeii in a deadly shroud of ash and noxious gas, a powerful earthquake shook the Roman city, destroying buildings and killing hundreds. But the industrious people of Pompeii quickly set about repairing the damage, restoring their beautiful city to its former splendor. Little did they imagine that something far more destructive was in store.Then, on the morning of August 24, A.D. 79, Vesuvius exploded spectacularly, sending successive, choking waves of thick ash, hot rock and volcanic gas over the town throughout the day and night. Those who did not flee in time were suffocated, baked and buried in ash several feet thick.Today, the ancient city of Pompeii offers a detailed picture of life in a prosperous Roman town 2,000 years ago.Visitors can see a fascinating array of artifacts: intact rooms and furnishings, finely wrought bronze statues and haunting, well-preserved paintings and mosaics depicting people so full of vitality that one can't help but feel an affinity for those whose lives ended in such agony. Detailed plaster casts of victims can still be viewed, an eerie reminder of those lives cut short.Alas, ancient Pompeii is threatened again -- this time by an excess of visitors and a succession of floods in recent years that have done extensive damage to some of its most famous sites, some of which have now been closed to the public.For further inspiration in planning your visit, you might go see "Pompeii," a new 3-D movie depicting the city's final hours. www.pompeiturismo.it.15 ancient ruins you might not knowTiwanaku, BoliviaMore than 12,500 feet in the Bolivian Andes near the shore of Lake Titicaca, this mysterious, pre-Incan city was once the religious and political center of the Tiwanaku culture, which ruled a vast Andean empire. Archaeologists generally place its origins around 1200 B.C., but some believe the city could be far older.Whatever the case, the Tiwanaku (also spelled Tiahuanaco) people were flourishing between A.D. 400 and A.D. 900. They left evidence of a society with impressive technological skill and a highly developed cosmology.Lacking beasts of burden, the people of Tiwanaku nonetheless managed to haul huge stone slabs, some weighing several dozen tons, for miles to construct religious temples and the towering monolithic statues that guard over them. The structures are built to astrological specifications to track the progress of the sun and mark seasonal shifts -- very important for an empire built on agriculture.Today, it's hard to imagine that this arid, treeless land could produce a bounty of potato, quinoa, corn and even peaches. The citizenry's collective effort to cultivate this land allowed it to flourish, and they reaped the rewards.The empire of Tiwanaku eventually expanded to include most of Bolivia, as well as territory in present-day Peru, Chile and Argentina. But during the 12th century A.D., the empire collapsed. The prevailing theory today is that climate change caused crops to fail, eventually destabilizing the government.One of the most iconic sights at Tiwanaku is the Puerta del Sol, an imposing rectangular portal wrought from a single 45-ton stone slab that stands atop the Kalasasaya Temple. It is carved with symbols representing a powerful god, as well as elements of an astrological calendar. The pyramid of Akapana is another must-see, along with the red sandstone pillars with carved heads, possibly representing the practice of publicly displaying severed enemy heads.Tour companies operating out of La Paz can get you to Tiwanaku in less than an hour. You can also visit the Regional Museum of Tiwanaku Culture to view collections of stone and ceramic artifacts. www.bolivia.travel.8 very old sites in the New WorldSkara Brae, ScotlandOlder than the Egyptian pyramids and Stonehenge, Skara Brae is a 5,000-year-old farming village along the white sand dunes of the Bay of Skaill, on the largest of the Orkney Islands. The best-preserved Neolithic village in Northern Europe was discovered in 1850 after a powerful storm roared through this archipelago north of the Scottish mainland.The houses are set into large mounds made of midden, or household waste. Part of the reason so many details of the village are known today is that the furnishings, like the dwellings themselves, were often made of stone.Many of Skara Brae's archaeological contemporaries are not nearly as well-preserved because their structures were made from wood. Not so here on a windswept island, where wood was hard to come by.After thousands of years of habitation, research suggests that climate change, perhaps responsible for brutal sandstorms, might have led the villagers to abandon the settlement around 2,500 years ago. www.historic-scotland.gov.uk.Mesa Verde, ColoradoIn the stillness of a summer evening in Mesa Verde National Park, it is fascinating to contemplate the network of villages that once stretched across the Colorado Plateau.For 700 years, starting around A.D. 600, the Ancestral Puebloan people, also referred to as the Anasazi, lived atop tree-dotted mesas and in elaborate, multistory buildings constructed into the sides of sheltering sandstone cliffs. More than 4,000 archaeological sites have been discovered here, and new discoveries occur regularly.Sometimes exceeding 8,000 feet, this was a harsh environment in which to build a civilization. People had to survive hot summers and freezing winters. The Pueblo people hunted and farmed corns, beans and squash and developed innovative ways to store water, including reservoirs and dams.But by A.D. 1300, it appears that their advances in irrigation and agriculture were insufficient in the face of a decades-long drought that dried up precious springs. This, perhaps in combination with environmental degradation and political pressures, may have caused the Ancient Puebloans to abandon their magnificent mesas.Several of the Mesa Verde cliff dwellings can be toured, including the 150-room Cliff Palace and Long House, as well as the Spruce Tree House and Balcony House.Of those, only the Spruce Tree House allows self-guided tours; to see most of the major cliff dwellings, visitors must take a ranger-led tour. Information about tours and the history and ecology of the park are available on the park website. www.nps.gov/meve/index.htm.Petra, JordanIt's not hard to understand why Petra is one of the world's most famous archaeological sites -- made even more so by its appearance in the 1989 film "Indiana Jones and the Last Crusade." Enclosed by mountains and sheer rock, the city was carved out of massive cliffs of rose-colored sandstone 2,000 years ago by the Nabataeans, an Arab tribe.Despite its location in a barren desert prone to flash floods, the Nabataeans' sophisticated water system helped Petra survive and grow to become a major hub for trade routes linking China, India, the Mediterranean and the Middle East. In its heyday, massive trading caravans passed through the city.Petra eventually came under Roman rule, and a series of powerful earthquakes hastened its declined. It was eventually abandoned, although Bedouin tribes continued to watch over the magnificent ruins.To visit Petra, you must walk, ride a horse or take a horse-drawn carriage along the Siq road, a narrow passage of glowing rose-orange sandstone. At the end of the Siq is the magnificent Al Kazhneh, or "The Treasury," carved from a cliff and once believed to store untold riches. As the valley widens, the full splendor of Petra is revealed: elaborate tombs, eerie caves and an amphitheater constructed from the hillside. Two museums inside Petra display the city's art and artifacts. www.visitjordan.com.Knossos, GreeceFive miles inland from the coast of Crete, Knossos was the center of the Minoan civilization, a powerful Bronze Age culture that flourished between about 3000 B.C. and 1400 B.C. According to myth, the god Zeus had a son, Minos, who became king of Knossos.Among the many legends about King Minos is that his wife gave birth to the Minotaur, a man-eating monster who was half-human, half-bull. Daedalus, an Athenian craftsman, designed a labyrinth in which to trap the Minotaur, and was later trapped there himself.Although there is much scholarly debate about the existence and location of the labyrinth, the myths speak of the Minoan empire's regional influence. Fueled by trade and their mastery of the sea, Knossos to become an advanced city with running water, paved roads and fine art, including elaborate metal work, pottery and brilliant frescoes. But when the mainland Greeks finally seized Crete, the Minoan civilization had already begun to crumble. Why?There are competing theories about what exactly brought down the Minoans.Most involve a massive volcanic eruption on the nearby island of Santorini, which sent an explosive plume of gas and ash miles into the sky. Some scientists believe the force of the volcano caused a tsunami, and it may even have altered the climate. If so, the result for the Minoans would have been devastating: badly damaged infrastructure, the heart of its trading center destroyed, its crops ruined. Within a couple of generations, Knossos and the broader Minoan civilization was hardly capable of defending their territory.Among the many highlights is the Palace of Knossos. Sometimes characterized as a town in itself, it had a huge central courtyard, public baths with running water and hundreds of rooms that served as shrines, workshops, storage and living quarters for a king and his vast household. Copies of vibrant frescoes with dolphins and dancing ladies in the royal apartments are also not to be missed. www.visitgreece.gr.The lost city of AtlantisFor centuries, scholars have studied and debated the location of the lost city of Atlantis, which the ancient Greek philosopher Plato told was a city submerged beneath the sea overnight. But was this myth or fact? And if fact, where, exactly, does Atlantis lie? Theories have ranged from Cyprus, to North Africa to Santorini. (Remember the volcano thought to have brought down Knossos?)In 2011, an international research team grabbed headlines with the announcement that they may have discovered Atlantis in southern Spain, buried in the marshlands of Doñana National Park.Using specialized radar and under water digital mapping tools, they found evidence of prior human habitation and suggested that this could be Atlantis, claimed by the sea during an ancient tsunami. Although the theory was strongly rejected by some, the investigation continues.For travelers endowed with a bit of imagination, a trip to Doñana will be rewarding, regardless of the accuracy of the claim.For starters, the park is less than an hour's journey from Cadiz and Seville, two historic cities that should be on everyone's bucket list. You won't get to walk among any ruins, but this UNESCO Biosphere Reserve, with its rich diversity of birds and other wildlife, is an impressive setting in which to contemplate a lost civilization. www.spain.info/en.(CNN)BakuDaily.Az