Morning view from the slopes of Montaña Machu Picchu. Even though some aspects of its history remain unclear, Machu Picchu is most commonly considered an Inca citadel in operation during the 15th and 16th Century. It has gained international attention in the early 20th Century and has been declared a UNESCO World Heritage Site in 1983. Machu Picchu is located on a ridge above the meandering Río Urubamba at 2430 m asl. The meander core behind the ruins is Huayna Picchu (2693 m).