In the chaos of Milan's swiftly-converting industrial quarter, one massive space has been set aside for contemporary art. "Merkaba" documents Hangar Bicocca's first installation, the seven title towers, from the prototype stage to installation by cranes and pulleys to the spotlight. Each precarious-looking spire of cement and lead boxes has a name of its own as well. "Falling Stars," "Sternenlager," "Die Sefiroth," "Tzim-Tzum," "Shevirat Ha-Kelim," "Tiqqun" and "The Seven Heavenly Palaces." Their towering silhouettes, some as many as 50 feet high, are as mystical as their titles suggest, but they also seem to make reference to all that is changing and staying the same in the city where they stand, home both to early sacred and secular towers and contemporary skyscrapers. Kiefer, known best for his reckonings with German history, proves that he can work the same alchemy elsewhere.