Visit the Gothic cathedral and take the rooftop for city views; iconic and central — book tickets or timed entry. Cathedral access and terraces generally open 9:00am–7:00pm (seasonal changes).
Stroll the elegant 19th-century arcade, window-shop luxury boutiques and view Teatro alla Scala; La Scala Museum is open 9:00am–5:30pm if you want to go in.
Regional train to Como is about 40–60 minutes; get an early start to enjoy the lake. Trains run frequently but check the timetable for exact departures.
Explore the square and basilica (Basilica opening times roughly 9:30am–5:00pm; mosaics and treasury may have separate hours); arrive early to avoid crowds.