Cuicuilco

Cuicuilco is an important archaeological site located on the southern shore of Lake Texcoco in the southeastern Valley of Mexico, in what is today the borough of Tlalpan in Mexico City.

Construction of the Cuicuilco pyramid began a few centuries BCE, during the Late Preclassic period of Mesoamerican history. The site was occupied until its destruction by the eruption of Xitle, sometime between 245 and 315 CE.

Based on its date of occupation, Cuicuilco may be the oldest city in the Valley of Mexico and was roughly contemporary with, and possibly interacting with, the Olmecs of Mexico's Gulf Coast region.

Source: Wikipedia