The best-restored and biggest ruins I saw are west of Trujillo at Chan Chan. The Tschudi Temple/citadel, located almost on the ocean shore, is a dramatic place where the Chimu people lived from around 1100 CE (AD). Not much is known about the people here, though we do know that the beginning of the end was in the 1470s. The Inca cut off the aqueducts that brought vital water from the Andes to this dry place, and the Chimu could either be destroyed or assimilated. When the Spaniards got here in the 1500s, there were only ruins.
(Yup, it's nap time in the mid-day sun... for dogs and for people.)
(These photographs are Copyright © 2005 by Jerry Peek. Much higher-resolution versions of most images, and many other images too, are available at Jerry Peek Photography. Photos are available at reduced prices, or free, for non-commercial use.)