The eye and the intellect play off one another in surprising and beautiful ways in the art of M.C. Escher. Where the Renaissance masters used shading and perspective to create the illusion of three-dimensional depth on two dimensional surfaces, Escher turned those tricks in on themselves to create puzzles and paradoxes. He manipulated our faculties of perception not simply to please the senses, but to stimulate the mind.
Via Luca Baptista