The 3D City Database is a free 3D geo database to store, represent, and manage virtual 3D city models on top of a standard spatial relational database. The database model contains semantically rich, hierarchically structured, multi-scale urban objects facilitating complex GIS modeling and analysis tasks, far beyond visualization. The schema of the 3D City Database is based on the City Geography Markup Language (CityGML), an international standard for representing and exchanging virtual 3D city models.

The 3D City Database has been realized as an Oracle Spatial or PostGIS relational database schema. It is shipped as a collection of SQL scripts which allow for creating and dropping instances of the 3D City Database on top of an Oracle Spatial or PostGIS DBMS.