This optical illusion is also known as an ambiguous object - an object that changes its appearance when reflected in a mirror.
Rounding Square from one angle looks like four overlapping circles. Viewed from the opposite direction, it looks like four overlapping squares. If you place the object on the table and position a mirror behind it, you can see both shapes at the same time!
Created by Kokichi Sugihara, a Japanese mathematician and artist known for his three-dimensional optical illusions. His illusions, which often involve videos of three-dimensional objects shown from carefully chosen perspectives, have won a number of awards at the Best Illusion of the Year Contest.