Thanks for the comments, and again sorry for the very late reply.
The internal structure is built with those soccer plates, all attached using 2x2 plates on top and 2x4 plates on the bottom. A few 4x4 brick pillars hold them up and the top is covered in 8x8 plates and then covered again in brick. I can't take credit for the use of those soccer plates, since a member in my LUG came up with the idea. I'll try to get a picture up to explain it better.
Yes, those 2x2 tiles are supposed to be wood. I just had it covered in brown plate before, but I recently bought all of these tiles, so I decided to use them.
Thanks again for all of the comments!