A month of centenary anniversary celebrations has begun in Peru in honour of the re-discovery of Machu Picchu.
American historian Hiram Bingham of Yale Univeristy found the 15th century Inca city in the Andes in south-east Peru 100 years ago.
He returned to Peru in 1912 and 1915 with the support of Yale and the National Geographic Society.
The citadel now attracts almost 1 million tourists to Peru every year.
Machu Picchu has become a national symbol and generates tens of millions of dollars annually in revenue for the country.
In 2007, an agreement was reached between Peru and Yale University for the return of artifacts removed by Professor Bingham from the site.
Professor Bingham later served in the United States Senate. He died in 1956 and is buried at Arlington National Cemetery.