The Aztec Empire History The center of the Aztec civilization was the Valley of Mexico, a huge, oval basin about 7,500 feet above sea level. The Aztecs were formed after the Toltec civilization occurred when hundreds of civilians came towards Lake Texcoco. In the swamplands there was only one piece of land to farm on and it was totally surrounded by more marshes. The Aztec families somehow converted these disadvantages to a mighty empire known as the Aztec Empire. People say the empire was partially formed by a deeply believed legend. As the legend went, it said that Aztec people would create an empire in a swampy place where they would see an eagl