Software/Games to get out creative energy?

I would love to find some sort of game or software program that will be a good outlet for my creative energy. I want to build worlds and create buildings and that sort of stuff. Be a real architect of the virtual world I'm creating. Sort of like the game "Wurm" if you have heard of it. But I want to know whats out there. Anybody have any ideas or answers to this question? Anything at all will be much obliged! Thanks everyone!