Machu Picchu, with the peak Huayna Picchu behind it. Perhaps the most famous Inca site, Machu Picchu is situated on a mountain ridge above the Urubamba Valley in Peru. It was probably built as an estate for the Inca emperor Pachacuti in the 15th century, but abandoned soon after during the Spanish conquest of the Inca Empire. Although known locally, it was unknown to the outside world before being brought to international attention in 1911 by the American historian Hiram Bingham, and it is now an important tourist attraction.Photo: Martin St-Amant