Escher’s Belvedere Optical Illusion
In Escher’s Belvedere Optical Illusion if you look at the beams they cross over from front to back, but how do we know which is the front and which is the back? This is physically impossible in a 3-Dimensional world but in 2d can give an alternate reality. If you notice the piece of paper on the floor (bottom left) shows a 3d cube almost as a clue to the belvedere’s structure. The man on the latter climbs from inside the gate in the lower platform then ends up on the outside above even tho its straight up!