Milan.

I've stayed at Hotel Gran Duca di York on 2 different trips. I like it because it's literally 5 minutes walk to the Duomo and across the street from the Pinacoteca Ambrosiana. It took me about 30 minutes to walk to the Last Supper with a little side stop at an archeological dig on the way, lol. The rooms are lovely, staff is nice in the extreme, breakfast buffet is terrific and I'd return there in a heartbeat.

https://www.ducadiyork.com/en/hotel-milan-city-centre/1-0.html

I stayed in the London Hotel (yes, there is a hotel in Milan called the London): https://www.hotellondonmilano.com/en/index.php. It's a basic, no frills hotel, but it's centrally located in the center of Milan near the Duomo.