We had a great stay at Olga's. The flat is original in its design and very nice. All was clean and well-equipped. The AC works very well. On Roman standards, the streets are very quiet and we had no trouble sleeping.
The place is 30mn away from Piazza del Popolo by walking, 15 mns by bus. But we used the bicycles included for free in the rental cost, which was very practical to go around (careful though, Roman roads are not well-adapted for cycling, especially large avenues).
Olga is a great host, very efficient and helpful, ensuring that all goes smoothly.
On the negative side: the flat is located one floor below ground, meaning the flat is a bit dark even if there are windows. But it didn't bother us, since we were out most of the time.
All in all a great experience and a very good place. Thank you Olga.