Modeling and visualization of city scenes is important for many applications including entertainment and urban mission planning. Models covering wide areas can be efficiently constructed from aerial images. However, only roof details are visible from aerial views and ground views are needed to provide details of the building facades for high quality fly-through visualization or simulation applications. Different data sources provide different levels of necessary detail knowledge. We need a method that integrates the various levels of data. We propose a hierarchical representation of 3D building models for urban areas that integrates different data sources including aerial and ground view images. Each data source gives us different details and each level of the model has its own application as well. Through the hierarchical representation of 3D building models, large area site modeling can be done efficiently and cost-effectively. This proposal suggests efficient approaches for acquiring each level model and demonstrates some results of each level including the integration results.