Machu Picchu National Geographic again and with the full support of Peruvian President Leguia. The expedition undertook a four-month clearing of the site with local labour, which was expedited with the support of the Prefect of Cuzco. Excavation started in 1912 with further excavation undertaken in 1914 and 1915. Bingham focused on Machu Picchu because of its fine Inca stonework and well-preserved nature, which had lain undisturbed since the site was abandoned. None of Bingham's several hypotheses explaining the site held up. During his studies, he carried various artifacts back to Yale. One prominent artifact was a set of 15th-century, ceremonial Incan
Machu Picchu prevent it from running down the mountain. Similar layering protected the large city center from flooding. Multiple canals and reserves provide water throughout the city that could be supplied to the terraces for irrigation and to prevent erosion and flooding. The Incas never used wheels in a practical way, although their use in toys shows that they knew the principle. The use of wheels in engineering may have been limited due to the lack of strong draft animals, steep terrain and dense vegetation. The approach to moving and placing the enormous stones remains uncertain, probably involving hundreds of men to