ABSTRACT
Over many centuries, two “poles” of Andean civilization developed, the one along the north coast of what is now Peru, the other in the south-central Andes. Only the Inca succeeded in joining the two into one vast empire. The northern pole was centered on the bleak and effectively rainless Peruvian desert plain, which extends south nearly 550 kilometers (350 miles) along the coast as far as Collasuyu, reaching a width of up to 100 kilometers (62 miles) in the area of the Lambayeque River. Some forty rivers and streams fueled by mountain runoff
flow across the plain, but they can be used for irrigation only in areas where the surrounding desert is low enough.
