What to do in and near Bonn:

- check what kind of exhibitions are on at the Bundeskunsthalle, they are usually really good

- Deutsches Historisches Museum, if you're into history

- Beethoven's birthplace

- a hike up the Drachenfels to enjoy the view and see the castle ruins. Drachenfels is the one of the Siebengebirge mountains that's closest to the Rhine.

- Brühl palace and park, if you like baroque style

For day trips:

- no need to mention Cologne, I suppose!

- Rhine valley between Koblenz and Bingen, no need to mention that either

- Ahr valley, with the spas of Bad Neuenahr, the old town of Ahrweiler, the rocky part of the valley at Altenahr, a hike on the Rotweinwanderweg trail through the vineyards and of course sampling some of the local red wines. (Local train from Bonn Hauptbahnhof every hour, direction: Ahrbrück)

- Aachen

- the Mosel valley, IMHO more romantic than the Rhine valley, and less crowded