No matter how much I tell myself this picture consists of two circles, my mind wants to see a spiral.

Is there a boat sailing in a pond in the middle of the street?

No, just some guy with a bit of chalk and imagination. Truly amazing what can be created with some imagination.

Yet another example where the lines appear to be curved, yet are in fact perfectly straight.

Behold! Levitation! oh wait its just some water on the ground. Such a simple trick but the effect is dramatic.

Okay prepare yourselves. These nuts will blow your mind. This is a cool illusion that you can do yourself if you have the time, using color and perception you can do some crazy things.