Machu Picchu law of Peruvian antiquities. In 2007, Peru and Yale had agreed on a joint traveling exhibition and construction of a new museum and research center in Cusco advised by Yale. Yale acknowledged Peru's title to all the objects, but would share rights with Peru in the research collection, part of which would remain at Yale for continuing study. On 21 November 2010, Yale agreed to return the disputed artifacts. The third and final batch of artifacts was delivered November 2012. The artifacts are permanently exhibited at the Museo Machu Picchu, La Casa Concha ("The Shell House"), close to Cusco's colonial
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