Forced to flee, in 1325 they went to a small island on the west side of Lake Texcoco where they began to build their city Tenochtitlan, eventually creating a large artificial island. It is said that the Aztec god, Huitzilopochtli, instructed the Aztecs to found their city at the location where they saw an eagle, on a cactus, with a snake in its talons (which is on the current Mexican flag). The Aztecs, apparently, saw this vision on the small island where Tenochtitlan was founded.