Rectangle and Square provides a comprehensive view of the holdings of Hermann and Margrit Rupf--one of the most important European collections of modern art, not least because many of the works were acquired in the year of their creation. Pieces by Hans Arp, Joseph Beuys, George Braque, André Derain, Lyonel Feininger, Lucio Fontana, Donald Judd, Ilya Kabakov, Wassily Kandinsky and many others are included.