GAM was one of Italy's first modern-art museums and has an astounding 45,000 works in its vaults dedicated to 19th- and 20th-century European artists, including de Chirico, Otto Dix and Klee. It's a great place to expand your knowledge of Italy's post-war period: Paolini, Boetti, Anselmo, Penone and Pistoletto are all well represented.