Nice optical illusions

Or should I say artistic ? There are done on the streets and on the building, truely wonderful :

This is a painting that looks 3-D from a certain angle. The artist is Kurt Wenner : http://www.kurtwenner.com/streetportfolio.htm

This is a painint on walls so that from a certain viewpoint it looks 2-D, simply amazing : http://www.2loop.com/3drooms.html