This optical illusion has been created in three dimensions. It is a real object. However impossible things seem to happen! The wooden balls seem to roll uphill. It cannot be magnets - they do not work on wood! This wonderful illusion was created by Koukichi Sugihara from the Meiji Institute for Advanced Study of Mathematical Sciences in Japan. In May 2010 this video was the winner of the Best Visual Illusion of the Year Contest 2010.
However once the structure rotates, we can see that it is not constructed as we initially thought. We might have thought that the wooden balls were rolling uphill. Once we view it from the other side, we can see that in fact the balls are rolling downhill, and that the laws of physics are still being obeyed. Whew!