Lodging and sights ... Frankfurt, Germany. We enjoy B&Bs... Will not have car so will get places either with tour guide, bus, or train.
Don't stay at the ramada near the train station seems nice and clean says 3.5 stars but it has bed bugs !!!!!! I would look online and stay somewhere closer to the central part of town near the church or the historic district not far from the river about 7 years ago
Try to do a tour of the Romantic Road to the medieval town of Rothenburg ob der Tauber, south of Wurzburg. South of Frankfurt is the famous university town of Heidelburg but it is a good bit south. West is the nice town of Wiesbaden and the Rhine. It would be worth taking a trip long the Rhine past the famous Lorelei Rock. Don't know Frankfurt that well as I've only transited there. about 7 years ago