Machu Picchu is an ancient Inca citadel set high in the Andes Mountains in Peru. It is one of the most significant archaeological sites in South America, containing well-preserved stone structures built in the 15th century. The site was built in the classical Inca style, with polished dry-stone walls. It was abandoned just over 100 years after its construction at the time of the Spanish conquest of the Inca Empire in 1532.