Boingboing posted this video of Prague’s Astronomical Clock’s 600th anniversary. They project 10 minutes of animation onto the face of the tower that causes it to build, fall apart, go through seasons, catch on fire—all sorts of crazy stuff. Check it out. (updated with higher quality video)
My favorite part is the very beginning of the animation, where the schematics trace the contours of the tower.
This isn’t the first time this has been done. Another really good one is Samsung’s that they did in Amsterdam to promote their new 3D TVs (I think):