an upright clown but a circus when turned clockwise

Above Viewed upright, it is a portrait of a clown. Rotate one turn clockwise, and it becomes a circus scene. Ambiguity. Double image. Puzzle picture. Hidden figure. For more on embedded figures and camouflage, go here. Artist unknown, from Larry Kettelkamp, Tricks of Eye and Mind: The Story of Optical Illusions, 1974.