Free Republic

Nabta Playa in Egypt is an ancient stone circle that researchers suspect was used to determine the summer solstice, which signaled rain was on the way.Today, its main stones are in a museum in Aswan to protect them from vandalism. But originally, Nabta Playa consisted of dozens of upright stones, each a few feet high, in the desert about 60 miles (100 km) west of the Nile.In addition to a pile of stones above a central tomb, many of the stones seemed to have been deliberately placed in a circle to align with the rising of certain stars.The circle's six...

For almost as long as we've had civilization, we've lost it. There are records going back hundreds of years of explorers discovering huge temples encrusted with jungle, or giant pits full of treasure that were once grand palaces. Why did people abandon these once-thriving cities, agricultural centers, and trade routes? Often, the answer is unknown. Here are ten great civilizations whose demise remains a mystery. 1. The Maya The Maya are perhaps the classic example of a civilization that was completely lost, its great monuments, cities and roads swallowed up by the central American jungles, and its peoples scattered to...