This spiky Gothic megalith sits like a giant marble porcupine in the very heart of Milan in front of its own pedestrianised square; of all sights in Milan, this one is absolutely impossible to miss. The world's third largest cathedral, covering 12,000m2, it took more than four centuries to build, from 1386 to 1813, after a final push from Napoleon. It also took six years to clean, the covers only coming off the buffed- up product in 2009. Inside is cold, dark and majestically Catholic, with 164 stained-glass windows, 52 towering pillars and room for a congregation of 40,000 (there's always room for respectful tourists at Sunday masses). Take the 160-odd steps up to the roof (or better still, the lift; open 9am-5.45pm, and 4.15pm in winter) for awe-inspiring panoramic views of the city (and the Alps on a clear day) through a gargantuan crown of 135 white marble spires. On top of its central spire, at 108m, sits La Madonnina ('little Madonna'), a gilt copper statue that is a point of reference for every Milanese. So important is La Madonnina that Mussolini decreed that nothing in Milan should be taller. In the 1950s, Gi`o Ponti's Pire- lli Tower trumped her; to appease the city, the tower was topped with a scale model of her so she still had the highest vantage point in Milan (at 127m). The Duomo's history is documented in the Museo del Duomo (Piazza del Duomo 14). Its epic construction has even acquired proverbial status: when something takes forever to finish, it's like 'la fabbrica del Duomo'.