This looks like a good (free!) 3d modelling application, particularly for hard modelling. In fact, if you want to make some contributions to the starport evolution by submitting a building of your own, you can use this. Did I say it looked good? I've just been having a play - It's absolutely superb and very easy to use.
Ravs
http://www.moi3d.com/index.htm
Ravs
Ravs
http://www.moi3d.com/index.htm
Ravs
