The most impressive part of the Rhine Gorge is between Koblenz and Mainz. While it's perfectly possible to do the cruises from Cologne, Cologne to Bonn is not the section people rave about. But I think if you get a pass you can get on and off the cruise boats as you wish and dip in and out of the little townships. Bonn is worth a short look-in - a pretty little city, compact and all painted in gelato colours, if a little sedate. Do a search on 'Rhine' here on Fodors and you'll get a lot of info on castles on the Rhine. You might also think about a trip on the Mosel which joins the Rhine at Koblenz, that's quite lovely too.

Lavandula

There is a pretty stretch of valley just South of Bonn, past the Seven Mountains and the islends of Nonnenwerth and Grafenwerth. There are cruises from Bonn to Linz, which is a nice small town, and back starting from Bonn. This is worthwhile if you are looking for a short cruise.
http://www.b-p-s.de/index.php?lan=en - if you click "timetable", the search function is set by default to exactly this cruise, so all you have to do is select a date and click the "Get trips" button. The departure point is on the river promenade next to the palace gardens (Hofgarten).

Anything North of Bonn is just flat ground and industry, not worth bothering. Sure, the most impressive part is further South between Koblenz and Bingen, but that means a full day trip.

Does anyone know how far it is from Bonn ferry station to Bonn train station by foot? We plan to use the Germen Rail Pass to take the ferry from Cologne to Bonn, but intend to take the train back to Cologne. We are traveling with baby, so we would like to know if it's possible to walk from ferry station to the train station. Thanks for reply~~

The station of the K-D is quite close to the railway station. Maybe 10-15 minutes and you can walk part of it through the pedestrian zone, combining it with some shopping or lunch.

For a look at the map: http://www.k-d.de/de/linienfahrten/anlegestellen/bonn/

I forgot one thing: there's a beer garden (Alter Zoll) on your way. It's directly at the Rhine and if the weather is nice, it might be an idea for lunch.

You can walk through the pedestrian zone, past Münster church, the palace (now university) and through the palace gardens in about 15 minutes and see these sights on the way.

Thank you for your help!!