Milan to TMB sightseeing suggestions

In late June I’m doing the southern half of the TMB. I fly in and out of Milan. I’m bookending the trip with 3 days to start and finish with no plans yet. Please share suggestions on can’t miss cities in that area.

I’ll do a night or two in Milan to start probably to get past jet lag but even where to stay in Milan would be helpful.

I’m thinking a day on the French coast might be cool as well.