Impossible figures: Schroeder stairs, impossible trefoil... (see, B.Ernst: L'avanture des figures impossibles, Taschen, Berlin, 1990).

Mosaics from Antioch (see, E.H.Gombrich: Art and Illusion, Phaidon Press, London, 1959).

Evolution of Thiery figure, tribar and other impossible objects from Koffka cube, and hexagonal "OpTiles".