Bonn/Bad Godesberg.... an old stamping ground of my youth.
My local knowledge is a little sketchy being as it's 35 years out of date
Guessing the Rhein road (we're heading south) through Koblenz is still a scenic ride/drive - at least as far as Rüdesheim...
Or head over the Ardenauer bridge to Königswinter.... some nice Rhein veiws from up at Burg Drachenfels....