Machu Picchu is a pre-Columbian Inca citadel located 2430 meters (8000 feet) above sea level. It's on a mountain ridge above the Urubamba Valley in Peru, 80 km (50 miles) northwest of Cusco and by the Urubamba River. It's called "The Lost City of the Incas". Machu Picchu is one of the best known symbols of the Inca Empire. They say it was forgotten for centuries. An American historian, Hiram Bingham called worldwide attention to the area in 1911. Since then, Machu Picchu has become an important tourist attraction. Machu Picchu was declared Historical Sanctuary of Peru in 1981 and a UNESCO World Heritage Site in 1983.