There is great difference between the real world and its images; the real world is three-dimensional whereas the images are two-dimensional. In spite of this difference we can enjoy visual media without any special efforts. Why can we do this ? This question can be partly answered by the study of depth illusion. It seems that the human brains try to recover the depth from images using strong performances for some special subclass of objects such as rectangular solids. This observation also suggests fragility of the visual media culture. We discuss this point using optical illusion raised by impossible objects and impossible motions.