Apotzonalco, but it only flows during the rainy season as do a number of arroyos. However, there are a number of underground water resources, which supply the municipality with potable water. Most of the residents of the municipality earn a living through farming and/or livestock raising, producing corn, cattle and domestic fowl. Some fruit, principally capulins, tejocotes, and peaches are grown. About two-thirds of this is for local consumption. There is little industry and commerce here. What is here is limited to the needs of the farming community. About six kilometers north of the municipal seat is the Chucoatl Ceremonial Center, which is located on an ejido. It is an archeological site with petroglyphs, a stone serpent's head and an etched hydraulic map. The serpent's head is placed such that, at the solstice, the sun rising over the “neck” of the Iztaccíhuatl volcano (which resembles a sleeping woman) shines its first rays of light on it. It is thought to have significance with the fertility of the land. Another pre-Hispanic complex is located by the Cuajoma Mountain. The sites have several layers. Some date from the fall of Teotihuacan in 1600 AD to the occupation of the area by Chichimeca tribes in the 13th and 14th centuries. Artifacts found at the surface date from 1400 to 1521 AD. There is a research site dedicated to investigating atmospheric conditions, in particular the effects of air pollution in nearby Mexico City. It is the only center located to collect data from times when the wind blows south away from the city. In particular, nitric oxide levels are measured here. Towns and villages The largest localities (cities, towns, and villages) are: References Municipalities of the State of Mexico Populated places in the State of Mexico