Well I've got a cardboard box fort rocking out in the living room if that counts.
Unpacking is boring, therefore fort building is required.
Dream castle: Plutonium outer layer kills off anything nearby, or the planet if someone decides to sling a rock at my plutonium/lead lined window. Then a nice layer of lava, just for... umm... security? just incase they de-doo-dah my plutonium? Nah, it's awesomeness I'll go with that. Then a lead inside wall. Maybe some wall paper...
Seeing as I'm not going to beable to go outside with out getting atleast a little cancerous, I may as well have a few houses on the inside wall made of cake, pie, chocolate, bacon. So I can eat them an evict the tenants into a radioactive outer world. Inner sactum has to have a pool though... maybe a zero G chamber. AND BE MADE OUT OF MARSHMALLOWS!