Duomo di Milano

Milan's cathedral took nearly six hundred years to finish — begun 1386, façade completed under Napoleon's impatient orders in 1805, the last details signed off in 1965 — and the city's dialect coined a phrase from it: "fabbrica del Duomo," a project that never ends. The result is the largest church in Italy (St Peter's is technically in another country, as Milan enjoys noting): a Gothic forest of pink-veined Candoglia marble carrying 135 spires and around 3,400 statues, crowned by the golden Madonnina at 108 metres, above whom no Milanese building was allowed to rise for a century (the skyscrapers that finally did carry replica Madonninas on top, by way of apology).

The interior is vast twilight — five naves under 45-metre vaults, the largest stained-glass windows in Christendom glowing at the apse, and the macabre star exhibit of St Bartholomew flayed, wearing his own skin as a scarf (the sculptor signed it defensively: "not Praxiteles, but Marco d'Agrate"). But the Duomo's unique selling point is the rooftop: no other Gothic cathedral lets you walk its actual roof terraces among the pinnacles, flying buttresses at hand height, the Alps on clear mornings behind the Madonnina. Sunset up there, with the piazza swirling below, is Milan's single best moment.

Ticket logic: the culture pass tiers run from church-only to church-plus-rooftop (stairs or elevator) plus museum and the San Giovanni baptistery ruins below the floor. The rooftop-inclusive ticket is the correct buy; the elevator saves 250 steps for a small premium. Book the timed slot online — the piazza queue in season is brutal — dress code enforced (shoulders/knees), and go either at 9 AM opening or for the last rooftop slot before sunset. The €0 companion piece: the Galleria Vittorio Emanuele II arcade alongside, where spinning your heel on the mosaic bull's worn-away anatomy is the city's luck ritual and watching others do it is free theatre.