Good construction sandbox game?

I have sweeped through Google but can't seem to find a good sandbox/construction game. What I mean is a game like Forge in Halo Reach, but more directed toward it. No storyline, just you in a world building things. Not a cubey game like Minecraft, i dont like those as much. I would like if it had a little destruction in it too. I would like this because it would be cool to build a base, and different things like that. PLEASE help me find one it seems impossible!!

BTW i have a steam account so it can be on steam

Do you mean something like Grav? Which unfortunately isn't out yet. A lot of these types of games tend to be the blocky type, so it is a bit difficult to suggest anything. Maybe planet explorers, although that is more of an exploration game, hence the title. Starforge was supposed to be pretty much what you were looking for but that got really bad user reviews on steam.

You can build stuff on Just Cause 2 Multiplayer.

Try Jman100s freeroam construction sandbox server

Here are some examples (all player created)

Here's a video of a rollercoaster my friend made:

GarysMod

Project Spark ?