Anamorphic Illusions

I just have to share this great link to the work of UK-based artist Julian Beever:

http://users.skynet.be/J.Beever/pave.htm

One example of his many 3D sidewalk drawings is below. I've never seen one of these in person, but it seems that to achieve the 3D effect the pictures are wildly distorted and must be viewed at just the right place/angle. Some of the photos on the site were taken from different places so you can see how the perspective is achieved.