How to support spatial objects in a 3D-GIS for urban planning

3D techniques are more and more used in the field of urban planning. Therefore 3D city models are generated with a lot of expenditure. Software systems are available for that purpose. However, queries in the field of GIS, concerning the geometry, topology and thematic data, cannot be satisfied by these systems. Furthermore, they do not generally support the third dimension.This paper describes a data model that joins the advantages of a GIS and the third dimension for queries and presentations. Based upon this data model an object-oriented prototype is realised. The whole three-dimensional query spacecan be used for inquireis regarding topology and geometry. Textures, a digitalelevation model and complex 3D objects are available to generate multiple presentations. Several presentations of the objects can be designed flexibly and easily with the proposed data model. As all objects manage their presentations on their own a simple version management or a level of detail can be introduced.