Cuicuilco was one of the most important sites of the Preclassic era (1500 BC – 250 AD) in the Valley of Mexico, as this was where the first monumental architecture appeared, of a kind limited to major regional centers. Another distinctive feature is the shape of its pyramids. Both the Great Pyramid and the Mound of Tenantongo in the modern-day Bosque del Tlalpan park, are semi-circular in elevation, like truncated cones. This architectural typology has not been found in any other settlements of the same era. Some of the smaller structures also had the same form (Cuicuilco C and the Mound of Peña Pobre).
The apogee of Cuicuilco was between 200 BC and 250 AD, when it is estimated to have covered 1,000 acres and had a population of around 20,000. The urban center also boasted ritual buildings, platforms, houses for the rulers, significant hydraulic works, agricultural land, and living quarters—ranged around the city’s main nucleus—for the commoners. Cuicuilco is likely to have been the principal town with a number of smaller surrounding settlements; it would have probably controlled not only the local resources but also access to the trade routes to the valleys of Morelos and Toluca, as well as routes to the south-east and west of the Valley of Mexico from the south-west.
Today we only have a small area of archeological evidence—approximately 150 acres—of Cuicuilco’s remains, since the lava from the Xitle volcano blanketed part of the ancient city. This event took place in around 250 AD, and resulted in the abandonment and decline of this Preclassic settlement. In this area we can still observe some of the buildings, including the Great Pyramid, the Stela, Structure E-1 and the Kiva (Cuicuilco A), Structures II, VI, VIII and IX (Cuicuilco B), the Mound of Peña Pobre and the Preclassic Canal (Cuicuilco D), as well as the Mound of Tenantongo (in Bosque de Tlalpan park). Structures I, III, IV, V and VII (Cuicuilco B) and a circular structure in Cuicuilco C (all now destroyed) are the most notable constructions to have been discovered that also formed part of Cuicuilco.
