While reading about the way the anatomy of the eye relates to the perception of the outside world, I was intrigued by the idea of optical illusions. My favorite optical illusion is the rotating hollow mask. My first experience with such an illusion was at the Franklin Institute in Philadelphia. In one of the areas, there was a hollow dragon sculpture. What was amazing was that when you looked at the dragon from a certain angle, it appeared to be three-dimensional. I took the opportunity to research this illusion for this blog.