Machu Picchu is a 15th-century Inca citadel situated on a mountain ridge 2,430 meters above sea level. It is located in the Cusco Region, Urubamba Province, Machupicchu District in Peru, above the Sacred Valley, which is 80 kilometers northwest of Cusco and through which the Urubamba River flows. Most archaeologists believe that Machu Picchu was built as an estate for the Inca emperor Pachacuti (1438–1472). Often mistakenly referred to as the 'Lost City of the Incas', it is the most familiar icon of Inca civilization. The Incas built the estate around 1450 but abandoned it a century later at the time of the Spanish Conquest. Although known locally, it was not known to the Spanish during the colonial period and remained unknown to the outside world until American historian Hiram Bingham brought it to international attention in 1911.