Front image of The Thing taken at PS 37 in The Bronx. Click ‘side view’ to see the other view.
Photo by Martha Cooper.

Magic Eye makes useful optical illusions too…corporate signs! I mean it’d be bad if you actually wanted to read it, but it looks so cool!

they installed these optical illusion speed bumps in Philly to trick people into slowing down, and supposedly it’s working
(check out the accompanying NYTimes article linked to below the pic)