The so-called Cafe Wall Illusion has been described as a...

The so-called Cafe Wall Illusion has been described as a checkerboard with the squares slightly jumbled or off-kilter. The alternating light and dark squares do not line up directly with the squares on the rows above and below them. The result is that the horizontal lines in between each row appear to be slanted. In reality, the horizontal lines are perfectly parallel with one another and totally straight.