Mel Gibson says Apocalypto, his new movie set during the collapse of the Maya Empire, should not be seen as a historical document.

At least one expert couldn't agree more.

Though it gave rise to awe-inspiring architecture and surprisingly advanced science, the Maya civilization—which thrived in what are now Mexico, Guatemala, Belize, and Honduras—began declining around A.D. 800.

Archaeological evidence points to a multitude of factors that could have led to this decline, including internecine warfare, the loss of trade routes, drought, and disease.

But before the fall, the Maya ruled the region from seats of power in dozens of cities. It is this so-called Classic period [A.D. 250 to 900], and especially its end, that the film most resembles, though no date is