A flat, two-dimensional circular chess game board, that is adapted for playing chess, is shown having a playing area of circular configuration that is divided into a plurality of alternate light and dark playing spaces by means of an inner circle having a pair of diametrical flaps at the East and West...http://www.google.es/patents/US4322085?utm_source=gb-gplus-sharePatente US4322085 - Circular chess game
