This page provides some of the cool and classical optical illusions.
This is an example of an illusion that occurs due to looking at the same object from different perspective. You can either see an ordinary vase or see two people facing each other.
The famous cube that we draw in geometry can have two perceptual interpretations. I we consider the pink colored surface as being closest to you, you could think of the cube as being either going into the plane or coming out of the plane.
Depending on which coloured surface is closer to you, the image can have completely different interpretations.
Old Woman Young Woman
This is a very famous picture used to explain the human perceptual process. Some people perceive this as an image of a young woman while others see an old woman. The young woman can be seen as if she is looking into the plane and is wearing a red necklace. However, if you consider the necklace as lips, you can visualize the side view of an old woman. The more time you spend looking at the picture, the more likely you are to shift perspectives.