I highly recommend Luisa & Gerardo's place. The location is superb as it is only about 15 mins away from the train station (on foot). It is also located in central Bologna and very near the restaurants and historical sites. The apartment itself is fantastic. It is very clean and well-decorated, the furniture is of high quality, and it is quiet at night with almost no noise at all. Check-in was very convenient and Luisa was very responsive.