Google Sketchup

A useful tool I use when making buildings is Google Sketchup, not only is it free, it's very easy to use. Very quickly you can get an idea of what your building is going to look like when completed, exact measurements can be inputted allowing a true scale model.




This took me about 30 minutes most of that figuring out how to make a dome, there is also an extensive help library.

http://sketchup.google.com/