There are also these, http://www.bricklink.com/catalogItem.asp?P=30072, that are literally a raised platform, but I’m pretty sure that is the largest size they come in.
Pittsburgh Area’s Adult LEGO User Group
There are also these, http://www.bricklink.com/catalogItem.asp?P=30072, that are literally a raised platform, but I’m pretty sure that is the largest size they come in.