PERU: The Chimú civilization had a long-standing conflict with their neighbors the Incas, resulting in the 15th-century Chimor-Inca War. It had been thought that the Chimú built a 6-mile-long, 8-foot-high earthen wall across the desert that separated their territories to protect against Inca invasions. New research on the wall, known as the Muralla La Cumbre, has determined that it was actually constructed centuries earlier, around 1100, to keep floods caused by El Niño weather cycles from ravaging the Chimú’s fields.