The 3D Geoinformation Group of the Delft University of Technology has released a QGIS plugin for the 3D City Database. This allows CityGML data from the 3DCityDB / VC Database to be loaded and used as different layers in QGIS. The tool supports the display of the data in 2D and 3D as well as the editing of attributes. The plugin is the result of a master thesis and is freely available as open source.
Virtual City Systems accompanied the master thesis and supported the development.