Julian Beever is a pavement artist who has been drawing amazing pictures on the streets of UK, Belgium, Holland, Germany and the USA.
But for me, his optical illusions are just sensational. Take a look at some of his street drawings at http://users.skynet.be/J.Beever/pave.htm
Nice find.
I remember seeing the Batman and Robin image a while back and thinking it was so cool.
The guy is a genius (and I use that word sparingly).