Tourists walk among the ruins of the Machu Picchu citadel, 130 km northwest of Cusco, Peru on July 6, 2011. The Inca compound is being prepared for the centennial commemoration of its discovery by American adventurer and archaeologist Hiram Bingham in 1911. Machu Picchu recognized as a World Wonder in 2007 sits at 2,350 meters above sea level in the heart of the Urubamba valley in southern Peru, 510 kilometers south of Lima. The complex which remained unknown to Spanish conquerors is now visited by up to 250,000 a year. AFP PHOTO/Cris BOURONCLE (Photo credit should read CRIS BOURONCLE/AFP/Getty Images)
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