Geographic Information Systems (GIS) data models are abstract representations of geographic reality. The data model enables digital representation of geographic information within a database for various analytical operations to be performed using a GIS. Navigation in the urban environment involves multiple modes of transportation requiring complex decision making. The present thesis develops an object-oriented data model to represent a multi-modal urban transportation network that can be used for navigation and to perform other network analyses in urban environments. The data model divides the urban transportation network into two main parts, one being the network for modeling movement inside the buildings and the other being the network outside the buildings using multiple modes. The network inside the building is three-dimensional (3D) in nature, thus requiring to model vertical connectivity among floors. Such 3D network inside buildings is modeled using the existing 2D data structures and 3D visualization techniques available in commercial off the shelf GIS software. The network outside the buildings is modeled as a multi-modal network consisting of modes such as streets, walkways and public transit. The data model is implemented for the high-rise buildings and transportation network on the north campus of the University at Buffalo. The effectiveness of the data model is evaluated by performing path finding analysis in the study area using the data model with standard and customized GIS software tools.