A number of commercial software packages support CityGML.
Software
Software systems that provide CityGML support
CodeSynthesis XSD - an open source (GPLv2 plus commercial license), cross-platform XML data binding compiler for C++. Supports generation of the object model as well as parsing and serialization code from CityGML schemas. For more information on using with CityGML, see this wiki page.
tridicon™ CityDiscoverer - software suite and authoring tool for visualization and analysing large scale 3D city and terrain models.
GO Publisher WFS - An OGC Compliant schema translating WFS capable of serving CityGML from any given relational model / bespoke 3D geometry model.
BS Contact Geo 3D software from Bitmanagement for the visualization of GIS and geo-data with CityGML support.]
CityGRID Software for management and editing 3D city models from Met Geo Info.
CityServer3D Software suite for data management of 3D city models. Implements different standardised interfaces like CityGML, X3D, KML, WFS, W3DS. Geospatial information is stored in a database which enables scenario-based querying and visualization.