I've always wanted to paint a roughly square room with a map of the world... projected from the INSIDE. Like you were standing at the center of a globe, looking out at transparent walls.
Above you is the Arctic. Below you is Antarctica.
In the middle of the room I'd have a lamp, with a half-silvered bulb, that would rotate 365 degrees every 24 hours, so I could always just walk into the room and see the Terminator line... where the Sun was rising right now... where it was setting...
Man... I'd love that room.