Cuicuilco is an important archaeological Mesoamerican Middle and Late Formative (c. 700 BCE – 150 CE) period site located on the southern shore of the Lake Texcoco in the southeastern Valley of Mexico. Today, it is a significant archaeological site that was occupied during the Early Formative until its destruction in the Late Formative. 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 Olmec of the Gulf Coast of lowland Veracruz and Tabasco (also known as the Olmec heartland).
Based on known facts, it was the first important civic-religious center of the Mexican Highlands, its population probably included all social strata and cultural traits that would characterize the Altépetl (city-state) of classical Mesoamerica.
Cuicuilco was destroyed and abandoned since the eruption of the volcano Xitle, causing migrations and changes to the population, it culminated with the Teotihuacán consolidation as classical period ruler of the Central Highlands.
At the site are 8 of the many housing and religious buildings that once existed, and the remains of a hydraulic system that supplied water the city. One of the pyramids was built in a strategic position, representing early prehispanic attempts to link religious concepts with cosmic events through building construction.