Vincent J. Musi/National Geographic Stock

On a hill known as Göbekli Tepe (“Potbelly Hill”) in southeastern Turkey (see map), archaeologists have uncovered megalithic enclosures that date between 10000 and 8000 B.C.E., the dawn of civilization. These circular sanctuaries in the northern Fertile Crescent—the earliest ritual sites in the world—are causing experts to rethink the origins of religion and human civilization.