I stumbled upon this while wandering around a bit ago. These are hallways and rooms painted in such a way that from just the right angle it looks like there is a tinted lexan shape sort of floating in space. They are reminiscent of the guy that does perspective chalk drawings on sidewalks.
According to one of the BoingBoing posters they are the work of Felice Varini.
I think this is one of my favorites ... click the picture to see it from a different angle.


I know people with this kind of layout in their crib, but it takes a talented - and usually salty - painter to do it right.