We had a "Building Birthday" at our house. I made a state capital building cake - which would have been wrapped in a beautiful layer of fondant and had fondant windows put in if I hadn't just moved into our new house and been watching three extra children for four days. I'm still proud of it but it would have been incredible if I had finished it.
For some decorations I made some buildings out of Mega Bloks. I printed pictures of buildings my son would recognize on sticker paper, lined them up on the Bloks and cut out a portion of the picture for each block. I cut a small amount off between blocks so the stickers wouldn't be hanging off the edge. To help them last a little longer, I added a layer of Mod Podge on top. Each building was built in with a different color Blok. Along with the state capital, there was a temple, a smoke stack and our new house for him - and the rest of the guests - to build.