Most of what is today called Mexico fell under the domination of another great Native American civilization, the Aztecs. Their own myths place their origin at Aztlan, somewhere in north or northwest Mexico, where they lived as a small, nomadic collection of tribes.
During the 12th century A.D., the Aztec tribes migrated southward, settling in the central basin of Mexico by the 13th century. Their existence was a precarious one, as they were repeatedly attacked and routed by other groups. Finally, the Aztecs took refuge on small islands in Lake Texcoco where, in 1325, they founded Tenochtitlan on the site of present-day Mexico City.
From their new base, the Aztecs evolved into ruthless and well-organized warriors. By the 15th century, they subdued and subjugated the peoples of Mexico, thereby creating an empire second in size only to the Incas in Peru. Extending from the Gulf of Mexico to the Pacific and from the Valley of Mexico south into Guatemala, the Aztec empire was peopled mostly by slaves, whose work was supremely manifest in the capital.
As the conquistadors later noted, Tenochtitlan was a city as large as Cordoba or Seville; however, most remarkably, it was situated entirely within Lake Texcoco, two miles from the mainland, Four great causeways led to the city, which was watered by a system of magnificently engineered aqueducts. The streets, lined with splendid temples, issued onto great public squares, which served as marketplaces. And there were priests. Legions of black-robed holy men continually marched through Tenochtitlan’s boulevards, for the Aztec capital was the home of God himself as incarnated in the emperor, Montezuma II.