Teotihuacán, located in the eastern Valley of Mexico, is an immense urban site, covering approximately twenty square kilometers, that flourished between 100 B.C. and 750 A.D. The site, characterized by its immense size, unique grid-like organization, and dense population allows for the investigation of prehistoric urban planning issues such as resource allocation and water management. GIS-based modeling provides a means of investigating these issues on both an urban and regional scale.

The influence of proximity to water resources or sociopolitically important structures on the density of construction at Teotihuacán can be easily determined using structural density maps generated from a digitized site survey (Millon, 1973). Predicted structural density patterns were generated based on assumptions of an inverse relationship between density and distance to mapped water sources (rivers and reservoirs), and between density and distance to significant structures such as the Cuidadela and Pyramids of the Sun and Moon. These predictions were compared to structural density patterns generated by assuming either equal access to water resources or the lack of a strong, centralized political authority. The results of this analysis suggest that there may have been a water management system at Teotihuacán which provided water to the entire site and that proximity to the site center was also an important organizational factor.

On a more regional level, GIS-based watershed modelling can provide an indication of the sensitivity of surface water availability in the Teotihuacán region to factors such as forest clearance, urban construction, and climatic change. GIS can also be used to evaluate the spatial relationship between sites containing evidence of substantial obsidian production and obsidian outcrops. Digital elevation models of the region can be used to generate cost rasters which evaluate the relative effort necessary to travel between sites and lithic material sources based on the slopes which must be traversed. Thus, a variety of GIS-based analyses can contribute to an understanding of how access to resources can influence urban organization. Additionally, GIS-based analysis can be used to better understand how an urban site effects the surrounding region, in ecological, economic, and cultural terms.