Going to Begamo on Saturday. Looking forward to it. Have heard that Milan itself has two buildings worth seeing - the cathedral and the San Siro.
I lived just north of Milan for 3 years in the 90s. It's not particularly attractive apart from the centre around the Cathedral. Lots of nice places fairly close by, especially Lake Como if you have the time.
Bergamo is a hill top walled town that has expanded outwards from the walls. Its a beautiful historic old town within the walls but very modern outside the perimeter. Lake Como is only a train ride away if you have time.
I went years ago. Went into AC Milans ground and a walk on the pitch with Ronnie Glavin. His comment about the quality of the surface... "Not as nice as Oakwell"
My cousin lives in Bergamo, went to live there when he was karting at 16, stayed and got married. Ex World and European Karting champion.
I go a few times a year to watch Milan. Last there in May, going again after Christmas. Not the best Italian city, prefer Rome and Florence but there's enough to do, walk on the Duomo, shops & restaurants, San Siro, football museums, last supper (only if you pre-book in advance). It's got a really good nightlife to say they're Italian. We also did Lake Como, 45 mins on the train from Milan central. About a tenner return
If you're a Wes Anderson fan then a trip to the Prada Foundation is worth the effort for Bar Luce. link
My daughter lived in Italy for 8 months and loved her trips to Milan. But I will say this til the cows come home, Bologna was amazing. The sort of city that I would happily get a flight there in the morning and a late flight same day back home. And I would do that once a month til the day I croak. Food heaven.