In the 13th century, Aztecs resided in the south-central region of current Mexico. It is believed they arrived just after the fall, or helped with the victory over the previously dominating Mesoamerican civilization, known as the Toltecs. When they saw an eagle perched on a cactus in the marshy land, on the southwest border of Lake Texcoco, they knew that this was their place to stay. They considered it a sign from their gods. This swampy land was drained and they constructed artificial islands, called chinampas. On these chinampas, they planted maze, beans, tomatoes, squash, potatoes, and avocados. They also started building their capital city, Tenochtitlán.
The Aztecs located themselves in the central Mexican valley. This area was particularly swampy, as mentioned above, but it also was surrounded by jagged mountains and dry lands. Lake Texcoco was surrounded by swampland and yet, in the middle, it contained a dry island. It is on this island that they established their capital, named Tenochtitlan.