Nazca Desert (Peru)
Perhaps one of the most enigmatic locations in the world is Nazca where huge figures hundreds of feet across have been carved in the desert surface in ancient times. The symbols, sometimes in the form of animals and sometimes as abstract geometric shapes, were not rediscovered until the beginning of the twentiethcentury when airplanes allowed them tobe seen from the sky. Although some claim these figures were carved into the desert to allow the ancients to communicate with alien visitors from other worlds, most archeologists think they are sacred symbols meant to be used to worship the gods. Nobody is sure, so there is a real mystery here.
This prehistoric ring of giant stones and earthworks is thought to be about 4500 years old. Its construction has been credited over the ages to various agents including the wizard Merlin, prehistoric giants, the devil, and even alien astronauts. Engineers argue that the stones could have been moved using the primitive tools available at the time, but nobody is exactly sure how or why the work was done, leaving us a mystery. Scientists believe Stonehenge was constructed by a people with no written records leaving us with no direct evidence of what its purpose was so there is a multiplicity of theories. Even so, though, the ring clearly functions as an observatory and calendar as there is an alignment during the summer solstice and also with various phases of the moon.
The "Lost" city of Petra has a history that extends back into biblical times. The Nabataeans, a nomadic people, settled in the area around the fourth century BC. This part of Jordan has been carved by erosion into steep, rocky gorges and the Nabataeans used the walls of the canyons to carve magnificent facades for temples and tombs. The most famous of these, the Khazneh, or Treasury, was used as the exterior of the temple housing the Holy Grail at the climax of the film Indiana Jones and the Last Crusade. In its heyday, the city was a hub of trade. Nobody is quite sure when and why the city was abandoned and its final years remain a mystery even today.
Great Wall of China
One of the most spectacular sites in the world is the Great Wall of China snaking its way across the mountains. The first of the great walls dates back to 200 BC when the Qin Dynasty built a set of earthworks to keep out invaders from the north. However, the wall we are familiar with today, built of brick and stone,was mostly a product of the Ming Dynasty in the 15th century. The wall in many areas is about 25 feet high, 16 feet wide and has been restored in sections for the tourist trade. The total barricade with all its branches (if one includes earthworks and natural barriers such as mountains and rivers) stretches for some 5,500 miles.
Perhaps the mystery here isn't so much the wall, but how the urban legend got started that it was the only man-made object visible with the naked eye from the moon. This idea was a staple of trivia in such publications as Ripley's Believe It or Not dating back to the 1930s. The reality is that even though the wall is thousands of miles long, it's only a couple dozen feet wide at most and it can't even be seen from low earth orbit without binoculars.