[The Godfather]

The cafe wall illusion is an optical illusion, first described by Doctor Richard Gregory. He observed this curious effect in the tiles of the wall of a cafe at the bottom of St Michael's Hill, Bristol. This optical illusion makes the parallel straight horizontal lines appear to be bent. To construct the illusion, alternating light and dark bricks are laid in staggered rows. It is essential for the illusion that each brick is surrounded by a layer of mortar (the grey in the image). This should ideally be of a color in between the dark and light color of the bricks.