In Escher's Famous optical illusion of never-ending staircases, there is no answer. I believe that the answer is nether, I think that it is flat, not going up or down, because of the farther away stairs (Back) are not going up or down, you can see it when you look closely at them and block the other 3 sides out, and only look at the top of them. and if you look at the first front 3 stairs on the left side, and the 3 stairs on the right side, the last 3rd step on the left and the first back step on the right are on the same level to each other. and being that the back stairs are flat and the first back stair on the right is on the same back stairs, witch would make them all flat. If you have you own thought on it or comment please do so. It is hard putting in words so may be confusing to understand what I'm saying with it.