Machu Picchu, pre-Columbian Inca stronghold in the Andes, about 80 km (about 50 mi) northwest of Cuzco, Peru. Located at a high altitude on a ridge between two peaks, about 600 m (about 1950 ft) above the Urubamba River, the ruined city covers about 13 sq km (about 5 sq mi) of terraces built around a central plaza and linked by numerous stairways. The majority of buildings are one-room stone houses (now roofless), arranged around internal courts; some larger structures were evidently used for religious purposes. All are distinguished by engineering skill and fine craftsmanship. The city was discovered in 1911 by the American explorer Hiram Bingham; it is not mentioned in the writings of the Spanish conquerors of Peru, and the time of its occupancy is uncertain. Bingham believed that Machu Picchu might have been the last refuge of Incas from Cuzco fleeing the Spanish invaders, but nothing is actually known of its history.