Building Houses/Worlds in any game?

So, I'm searching for a multiplayer game where the player/players can create buildings and they can explore it with characters like in any game you explore a building. I don't care about the other specs of the game, just these two...

If anyone has any idea of a game like that, please share it with me.

Thanks for the help :)

P.S-not Minecraft

minecraft? sims 3? errr.. sim city is launching on march 5 does that count? xD

Rift has a nice housing/dimension system. Vanguard too. Check their videos.