Classic artworks

This sketch of endless staircase was painted by english bioligist Lionel Penrose in 1962. Earlier, in 1954 he and his son Roger Penrose published an article about impossible figures in the British Journal of Psychology, where they first described two basic impossible figures - the impossible triangle and the endless staircase.

The image was found at http://www.ucl.ac.uk/Library/special-coll/knowledge.shtml