following that link you will see enough different angles to see that the illusion is only workable from that exact angle - specifically look for the photo that shows the doorway on the ledge at the bottom of the spiral stair. (bottom row, second from the left)Originally posted by Shawn R. L.
It would be interesting to see that Escher building shot from a different angle. Could be that it\'s made to be viewed only from one angle for the \'trick\' to work.