While attending the Bridges conference in 2008, celebrating the 110th birthday of Escher in Leeuwarden in 2008 Karel was inspired by all the mathematical art in the exhibition and he decided to make a twisting in cellular concrete. Too much in a hurry he made a very fortunate mistake, he miscalculated and instead of making a twisting over 540 degrees he only twisted over 270 degrees. In this way he made a special variant of the so called Mobius band. If you follow the outer surface with your hand you may discover that the surface goes around four time before you reach the same spot . That makes this form unique because it has only 1 surface ( going around 4 times an no sides.