(Photo: Dominik Hartmann)
Father and son mathematicians Lionel and Roger Penrose devised the Penrose triangle--an impossible object that looks like a twisting 3-dimensional triangle. They and M.C. Escher also conceived of a staircase based on that design.
This staircase isn't quite like it, but like the Penrose triangle and stairs, there's no beginning or end. Ólafur Elíasson, a Danish-Icelandic architect, designed it for the Munich offices of KPMG, an accounting company.