We are building a system that can automatically acquire 3D range scans and 2D images to build geometrically and photometrically correct 3D models of urban environments. A major bottleneck in the process is the automated registration of a large number of geometrically complex 3D range scans in a common frame of reference. In this paper we provide a method for the accurate and efficient registration of a large number of complex range scans. The method utilizes range segmentation and feature extraction algorithms. Our algorithm automatically computes pairwise registrations between individual scans, builds a topological graph, and places the scans in the same frame of reference. We present results for building large scale 3D models of historic sites and urban structures.