I highly recommend Giulia and Nara's apartment. Within the old city ring road, it's an easy walk to Piazza Maggiore, conveniently located within a short walk of everything you might want - cafes and restaurants, supermarkets, laundromat, even a printing service (which we needed)!
The flat is very clean, as advertised and it was lovely to open the windows over terracotta rooftops in this old building. It was also quiet.
Giulia and Nara were super responsive and helpful, bringing around a couple of items we needed within an hour or two. They obviously care about the experience their guests have.
Would definitely return to enjoy this beautiful city again!