I was wanting to build the UESC Marathon from Bungie's Marathon series (90s FPS game fro the Macintosh). But according to the game, it's Mars' moon Deimos taht has been hollowed out into a colony ship. So, yeah, it would have to be huge.
In other news, I forgot my MacBook away from home and I'm using my iPhone a PowerMac G4 (circa 2001) as a team to conquer the internet. It's very tedious.