Tormentor asked about CityGen. It's a freeware application that creates nice urban scenes. It's currently in the v1.5 stage. You unfortunately need an older version of POV RAY - 3.02 - to render the scenes, and save them in some program like IrfanView. A lot of work - but it's a fun little program.
http://members.tripod.com/~dcieslak/util.html
There are other applications called CityGen, as well. One is CityGen V0.9, and uses VRML functions . . .