I guess we all have seen quite a few of those 3D paintings on pavements, which are so cleverly painted or drawn that they create - seen from one point of view - often clever and stunning optical illusions picturing fanstastic scenarios like vulcano craters or wormholes to other dimensions.
The artist John Pugh is the first that I have ever seen that does the same thing but on the walls of buildings. I amazed HOW realistic it looks.