I thought the walking tour offered by the Bologna Welcome tourist information office was good. I like that it is led by a salaried professional and not based on tips. Because it was raining, rather than standing outside for certain things, our guide got permission to bring us into some spaces in the city hall that are not usually open to tourists. I think being from the official city tourist office was an advantage there. If you will be seeing other paid entry sights in Bologna, the tour is covered by the Bologna card, or you can just book the tour. I signed up day-of in-person but you can also do it online. Also, for any questions the guide couldn't answer off hand, she offered to follow up if we returned with her to the information office.