My professor calls perspective drawings "lies" because really it's just a flat, 2 dimensional piece of paper that slanted lines are drawn on. Here's a collage of some cool sidewalk art pieces that fool the eye into thinking that there's actually depth on a flat surface:
The trick to these is that you have to be looking at them at just the right spot, or else the art will appear horribly distorted. Here's a comparison between looking at a piece from the right and wrong angles: