I still can't believe that a place like this exists, and that I had the privilege of staying in it. It's spectacular in every way.
As far as location: just look for the Duomo, and it is right there - literally. All roads lead to the Duomo and this place. You can walk everywhere, including the train station with suitcases in tow.
The apartment speaks for itself, but I do want to note that the owners are lovely people and went out of their way to accommodate our travel logistics. We didn't know until the last minute which train we would be taking, so they were very flexible in meeting us on our last minute train booking. They also were gracious in letting us stay a bit later before our departure train, since they didn't have an immediate need for the next guests.
We also only ate at restaurants they had recommended, and every recommendation was spot on!