Void Staircase by Guido Ciompi for The Gray Hotel in Milan, Italy This staircase cleverly builds upon an existing installation, and the hollow steps could easily be used as shelving. When viewed from a certain angle, each step appears to float in the 145
24 Insanely Clever Space Saving Interiors Will Amaze You
50 states bookshelf--This is cool, though wouldn't really work in a classroom. I think my kids would try to climb it. I could totally hear a "I'm almost in New York..." coming from the back of my room. Cute, though. Nifty idea!
Any slide for adults in a house is a great idea, but this one contains a water slide. Excellent choice of transportation and you can even get a shower on the way out of bed going down to get breakfast!