from Gizmodo by
Adrian Covert 
Aaron Tang's wall stairs are meant for living areas that are short on space, but they're so awesome that I'd want them even if I had 1,000,000 sq. ft. house. They work by having the frame of the stairs slide out from the wall, powered by hydraulic pistons, and having the stair planks fold over the frame one at a time. When finished, the stair frame slides back in the wall and the planks stand straight up, flush against the wall. Imagine, next time you're at a mansion/estate/castle party, you walk into the foyer to find no stairs at all. Then the owner hits a button on a remote and stairs appear from the wall. I'm pretty sure your mind would be blown. [Aaron Tang via Architechnophilia via TreeHugger]