This paper presents the integration of procedural modeling and geographic information systems (GIS) for the development of a 3D city model (3DCM), which is basically a computerized digital model of a city. Through a procedural approach based on computer generated animation (CGA) on GIS, the result of this work is 3D virtual modeling of urban areas originally without enough information of urban installations. Our system is capable of 1) detecting areas lacking this type of information, 2) through a sequence of rules-based algorithmic steps, modeling a complete city or part of a city, resulting in a 3D virtual model of the selected area. The final output of our system generates a high-precision and more complete three-dimensional urban environment based on two-dimensional vector data and terrain data in GIS, driven by semantic rules.