calling all italians (Luxembourg)

Hi all. I've got 38 days in Italy over summer. I don't want to rush so I'm thinking of just doing northern Italy and leaving Rome south to Naples for another time. I'm flying in and out of Milan, so I'm thinking of doing a loop. Milano - Verona - Venezia - Bologna - San Marino - Firenze - Genova - Como- Milano.
Any ideas? Places I could miss, places I shouldn't miss. (Been to Pisa before so might skip that).

Many thanks!