South America’s best-known monument, the citadel of Machu Picchu has been a UNESCO World Heritage Site since 1983 and the icon of Inca Empire. Located 2,430 metres up on mountain ridge, Machu Picchu was built in the 15^th century. No-one is really sure of its purpose, but many experts believe it was the retreat of the emperor Pachacuti. It was abandoned after 100 years and, although known locally, it was unknown to the rest of the world until it was found by explorer Hiram Bingham in 1911. Since then many a visitor has been enchanted by the mysteries of this incredible site.