Trompe l’oeil (Fooling the eye) is an artistic technique used to create anamorphic illusions, which use perspective constructions to generate what looks like a trick. You usually feel the effect while viewing it from a certain point. Swiss artist Felice Varini is arguably the best such artist in the world. If you still don’t get what I’m talking about…these images below will help you get an idea-
1) Viewed from the vantage point, it looks like a painted glass partition set in the corridor.
2) Viewed from another angle, you can make out the designs which lead to the illusion
He has implemented many such projects, even one which covered the entire port at the Cardiff Bay in concentric circles. Find more of these on his website (www.varini.org). Its entirely in French, so you’ll have to use your intuition a bit.