M.C. Escher

M. C. Escher, was a Dutch graphic artist. He is known for his often mathematically inspired woodcuts, lithographs and mezzotints. These feature impossible constructions, explorations of infinity, architecture and tessellations.

Ascending and Descending is a lithograph print by the Dutch artist M. C. Escher which was first printed in March 1960.
Cycle	House of Stairs
Convex and Concave It depicts an ornate architectural structure with many stairs, pillars and other shapes. The relative aspects of the objects in the image are distorted in such a way that many of the structure's features can be seen as both convex shapes and concave impressions.
Mosaic II
Drawing Hands It shows a sheet of paper out of which rise, from the wrists which remain flat on the page, two hands, facing opposite and apparently in the act of drawing one another into existence, a paradox.
Reptiles
Waterfall It shows an apparent paradox where water from the base of a waterfall appears to run downhill before reaching the top of the waterfall.
Relativity It depicts a paradoxical world in which the normal laws of gravity do not apply. The structure has three stairways, and each stairway can be used by people who belong to two different gravity sources. This creates interesting phenomena, such as in the top stairway, where two inhabitants use the same stairway in the same direction and on the same side, but each using a different face of each step; thus, one descends the stairway as the other climbs it, even while moving in the same direction nearly side-by-side. In the other stairways, inhabitants are depicted as climbing the stairways upside-down, but based on their own gravity source, they are climbing normally.