I thought this was really cool. Here is a series of photos taken in spaces where the walls have been painted to create a 3D illuuuusion. It only works when looked at from certain angles. Pretty compelling stuff. Not much utility in these, but awfully interesting to look at nonetheless. The one exception being a parking garage in Melborne, Australia that uses the effect to give drivers directional cues. I’d love to see more of these. Just don’t call them tricks. These Escher-esque designs are definitely illuuuusions, Michael.

Here’s a good series at moillusions.com (as I was looking at these, I discovered tons of other great illuuuusions at this site)

And here’s the Australian parking garage. This was a winner of several international design awards. Which ones though, I don’t know.