We describe a vehicle borne data acquisition system for urban environments and associated 3D data management and interactive rendering software. The data acquisition system is capable of acquiring 3D data from urban areas with centimetre resolution including automatic capturing of colour. The system includes a management and interactive rendering software which is designed to cope with the huge quantities of data generated by the acquisition system. It uses out-of-core preprocessing to transform data into octrees. Real-time interactive rendering is achieved by using novel techniques such as front-to-back octree traversal, occlusion query and speculative prefetching. The paper presents the results of the described techniques applied to large public areas including the City Centre of Verona, Italy.