Machu Picchu is an ancient Incan citadel set high in the Andes Mountains of Peru, above the Urubamba River valley. Built in the 15th century and later abandoned, the site remained unknown to the outside world until American explorer Hiram Bingham brought it to international attention in 1911. The extraordinary architectural achievement consists of approximately 200 structures arranged on a series of agricultural terraces, with a sophisticated drainage system that has withstood centuries of rainfall. The precise stone construction, accomplished without mortar and with blocks cut so precisely that a knife blade cannot be inserted between them, demonstrates the Incas' advanced engineering skills. Surrounded by cloud forests and dramatic mountain scenery, the site's remote location and mysterious origins have captured the imagination of travelers worldwide.