We decided to do the Basilica Administratum, since all the walls meet at 90 degrees. Here's what it looks like on their website.
My version will be slightly different. It will have less detail, but be about the same size and shape. I want a working door on one side and floors on which miniatures can stand at each level.
I started by designing one window in SketchUp.
I added more details to it, and then repeated it several times to make the building. For the "crumbling" parts of the building, I removed parts of the windows.
I then designed and added the columns on each side, and then added a door, and some floors at each level.
Here's my SketchUp design for the full model.
Each side is comprised of 3 layers of 1/8 material. I'll show the cuts and final product in later posts.