I'm looking for an open source GIS that supports viewing and editing of CityGML models.
So far, I've found a list of open source applications that support CityGML, but they all seem to be stand-alone applications, that don't integrate with common GIS systems: http://www.citygmlwiki.org/index.php/Open_Source.
I would also be interested in your experience with CityGML in a GIS (also commercial) context.
Best Answer
deegree3D (part of a broader FOSS geospatial project, deegree) looks like it might work for you. Probably depends a lot on what features you need. Unfortunately I haven't tried it, so I can't comment on its use or reliability.