I traveled together with another 5 girls and we had a nice stay at Alessandro's apartment. It's in walking distance from the Dome and from a metro stop and also from a bus stop, which connects you directly to the castle. The apartment is nice and clean and big so it's a good choice if you travel in a bigger group. Alessandro was also very helpful and allowed us to modify the reservation a week before our arrival and allowed us to checkin earlier than normal checkin time.