The Dutch artist M. C. Escher is known for his lithographs and woodcuts showing...well...things that look right, but really can't exist. They play games with perspective, and perplex even the most devoted rationalist. They just don't seem possible, yet there they are.
We find that many people can't "see" these, or need to stare at them quite a while before a slow, "Oh, yeaahhh....." emerges.
Tribar IAn impossible tribar floats lazily among the planets.
Impossible
Quilt
Based on a picture in a child's book on impossible designs.
AquariumAn impossible window frames an aquarium, while an impossible fish
swims
by.
Impossible
BlockAt first, this block seems OK, but...uh-oh...look at the corners!