Close_up of two kivas at Cliff Palace, an ancient Anasazi cliff dwelling in Mesa Verde National Park, Colorado. Kivas were circular, subterranean rooms used for ceremonial and communal purposes. Cliff Palace is one of six hundred cliff dwellings scattered throughout Mesa Verde and, with 150 rooms, it is the largest in North America, housing more than one hundred people at its peak. It is thought the Anasazi built cliff dwellings to defend themselves from hostile tribes living in the area. Cliff Palace was occupied for more about 100 years and was abandoned about 1300 A.D., possibly in response to a prolonged drought.