Machu Picchu, the 'Lost City of the Incas,' was built around 1450 at the height of the Inca Empire under the rule of Pachacuti Inca Yupanqui. Situated 7,970 feet above sea level in the Andes Mountains, the site is a masterpiece of 'ashlar' masonry, where stones are cut so precisely that they fit together without mortar. The city included temples, palaces, and farming terraces that were integrated into the natural mountain landscape. Machu Picchu served as a royal estate and a religious sanctuary. The Incas were unique among major civilizations for having no written language (using 'quipus' or knotted strings for record-keeping) and no use of the wheel for transport, yet they managed to build an empire that spanned 2,500 miles. Machu Picchu was abandoned roughly a century after its construction during the Spanish Conquest and remained largely unknown to the outside world until 1911.