The stately snowcapped peaks of Iztaccíhuatl and Popocatépetl rise behind the modern skyline of Mexico City. Built by the Aztecs in the 14th century on a series of islands connected by canals, Mexico City was seized in 1521 by Spanish conquistadors, establishing Spanish rule, which in turn was ousted three centuries later. Today, it is a vast metropolis with one of the world’s fastest-growing urban populations.