Chan Chan is the largest mud city in the world. It was built around 1200 A.D. by the Chimu people. About 25,000 people are thought to have lived in the city. At its most powerful, the Chimu Empire controlled all of the northern and many of the central coastal valleys of Peru. The Incas took control of the city in the late 1400s. (G. DAGLE ORTI—GETTY IMAGES)