I don't think that has been established yet. The Aztecs were originally a Nomadic Race when they came upon what is now Mexico City.
The pyramids that most folks associate with the Aztecs was actually very old when the Aztecs came upon them and were built by the Teotihuacan Culture.
According to Aztec Folklore, they followed a vision where an Eagle perched on a Prickly Pear cactus was holding snake in its claws. This location was Lake Texcoco and is now filled with dirt and is modern Mexico City.
Google the information for details...since this is a History Project. Aztecs or Aztec Folklore. Good luck!
