In the 1200's, the Aztecs traveled from Aztlan to the Valley of Mexico. However, they were considered bad, forcing them to work as mercenaries. Later, they worked in Azcapotzalco.
An eagle perched on a cactus eating a serpent was a sign given from the gods to the Atzecs meaning that they will live on a small island in Lake Texcoco. They were told from the priest of this.
The setting of Tenochtitlan was swampy and had limited space. In addition, in the island there were interconnecting lakes and forests and many animals in the city-state.
To make the area more convenient and pleasant, the Aztecs created canals and roadways and causeways to get to places, such as the mainland quicker. Although, sometimes the causeways and canals got too crowded.
The Aztecs traded and made Tenochtitlan a more powerful and better city. They found a new nutritious algae spirulina and made into a delicious food which they traded. They also trade salamanders, ducks, larvae of insects, and fish.
Through all the trade, the Aztecs (Mexicas) ruled and became a skilled group that lived satisfactorily. They lived and created things to from their surroundings.