In the few art classes I have taken in my lifetime, one artist always boggled my mind. Some artists have the ability to make you sit and stare at one a piece for a while, never figuring out how they could create such a thing. M.C. Escher had this ability.
This piece, entitled Ascending and Descending, looks like a normal building. However, the roof of the structure has been drawn in an impossible way. The steps are always ascending, however you always end up in the same place. But how can that be?
Escher, instead of using one vanishing point, has used two. Vanishing points are where lines in a scene meet and typical artists use only one. However, M.C. Escher was not a typical artist. He broke the laws of physics in his work and messed with his audience's monocular cue of linear perspective to create an impossible structure.