The architecture of North Italy developed in the 9th and 10th centuries. An association of trained builders, the Commacini, named from an island in Lake Como, flourished at this period. The best examples of this style are two churches: Sant' Ambrogio in Milan, and San Michele in Pavia. The eaves gallery built above the vault of the apse is a distinguishing feature. A fine example is the gallery in the central tower of the Cistercian church at Chiaravalle near Milan. A less pleasing characteristic is the false facade with its walls raised higher than the roof of the church, which became the prevailing form throughout Italy.