Take a look at the red lines on this picture. Which line is longer?

Is this knot pairing of triangles physically possible?

Look at the grouping of stairs below. How can they keep climbing?

This is an example of an anamorphic illusion created by julian beever. This sidewalk drawing was drawn in a special distortion in order to create an impression of 3 dimensions when seen from one particular viewpoint

Are you lookin at inside or outside of this magazine?

Despite their appearance, the top lines on each of these trapezoids is of  exactly same size!

Do you see a rabbit or a duck?

What do you see?
An old man or two people kissing?

Now look at the same image upside down.

Does this one make you dizzy?