This intricate Gothic structure has been fascinating and exasperating visitors and conquerors alike since it was begun by Galeazzo Visconti III (1351–1402), first duke of Milan, in 1386. Consecrated in the 15th or 16th century, it was not completed until just before the coronation of Napoleon as king of Italy in 1809. Whether you concur with travel writer H.V. Morton's 1964 assessment that the cathedral is "one of the mightiest Gothic buildings ever created," there is no denying that for sheer size and complexity it is unrivaled. It is the second-largest church in the world—the largest being St. Peter's in Rome. The capacity is estimated to be 40,000. Usually it is empty, a sanctuary from the frenetic pace of life outside and the perfect place for solitary contemplation.
The building is adorned with 135 marble spires and 2,245 marble statues. The oldest part is the apse. Its three colossal bays of curving and counter-curved tracery, especially the bay adorning the exterior of the stained-glass windows, should not be missed. At the end of the southern transept down the right aisle lies the tomb of Gian Giacomo Medici. The tomb owes some of its design to Michelangelo but was executed by Leone Leoni (1509–90) and is generally considered to be his masterpiece; it dates from the 1560s. Directly ahead is the Duomo's most famous sculpture, the gruesome but anatomically instructive figure of San Bartolomeo (St. Bartholomew), who was flayed alive. As you enter the apse to admire those splendid windows, glance at the sacristy doors to the right and left of the altar. The lunette on the right dates from 1393 and was decorated by Hans von Fernach. The one on the left also dates from the 14th century and is ascribed jointly to Giacomo da Campione and Giovanni dei Grassi. Although air pollution drastically reduces the view on all but the rarest days, the roof is still worth a look: walk out the left (north) transept to the stairs and elevator.As you stand among the forest of marble pinnacles, remember that virtually every inch of this gargantuan edifice, including the roof itself, is decorated with precious white marble dragged from quarries near Lake Maggiore by Duke Visconti's team along road laid fresh for the purpose and through the newly dredged canals. Audio guides can be rented inside the Duomo from March to December and at Duomo Point in Piazza Duomo (just behind the cathedral) all year long. Exhibits at the Museo del Duomo shed light on the cathedral's history and include some of the treasures removed from the exterior for preservation purposes.