As I mentioned a while ago, there isn't much Medieval to see in northern Italy except for some churches and monasteries, and some fortifications.
The wealth and urban renewal during the Renaissance is the reason. The narrow roads and alleys are often of medieval origin, but the old buildings are pretty much all Renaissance or later.
We did find one Medieval-era home in Orta San Guilio a couple of years ago (we drove our tiny rental over the mountains from Stresa for a day trip. I don't know how the lad fit his long legs into the back seat of that tin can, but he will put up with anything to explore new places):