This is really amazing. The squares marked "A" and "B" are the same colour
The so called-café wall illusion was first described by Gregory and Heard after seeing effect in the tiles of the wall of a café in Bristol. The lines appear to be bent but are straight (just hold a straight edge along them to prove it).
A blivet, also known as a poiuyt, is an undecipherable figure, an optical illusion and an impossible object. It appears to have three cylindrical prongs at one end which then mysteriously transform into two rectangular prongs at the other end.