Examination of aerial photographs of the Teotihuacan region for indications of abandoned irrigation canals revealed the traces of a small system just to the northwest of the modern road connecting the town of Atlatongo with the ceremonial center of Teotihuacan. The system lies along a stream flowing southeastwards in the tributary valley formed by Cerros Maravillas to the west, Tenextlacotla to the north, and Malinalco to the east (Fig. 123). The aerial photograph used had a scale of 1:10,000. It was taken by the Compañia Mexicana de Aerofoto and is identifiable as Sheet 50 of the aerial survey “Cuautitlan to Estacion de Irolo” (Fig. 124). Although the photograph was not taken for archaeological purposes, its utility in locating remains on the ground demonstrates once again that the systematic use of aerial photographs in settlement archaeology — used to such advantage elsewhere — could also yield promising results in Mesoamerica.