1100-1325 CE
From 1100 to 1325 CE, the Chichimecas swept down from the arid north into the Valley of Mexico — wave after wave of "dog people" as the settled folk called them, barbarians who learned the ways of civilization from the ruins of Tula and the survivors of Tollan. Among these migrants wandered an obscure tribe called the Mexica, searching for an eagle on a cactus, destined to build Tenochtitlan on that prophesied spot.