Bonn
Bonn is almost 2 hours from Wiesbaden, very near Köln. We went there not really knowing what we wanted to do or see and we paid for that. We got turned around a lot, and most of the attractions/museums we wanted to see were closed. The town is a university city and has the feel of one. There are large grassy areas dotted with students and book vendors all over the place. We saw some interesting churches and a nice little overlook to whatever river ran next to the city, but all in all it was sort of a long way to drive with little in return.
Köln
We went to Kü, or Cologne, via train with Nate's parents in March of 06. It was very cold and snowy, which made for a rather miserable day in March. We spent the majority of our time in the cathedral. We paid the extra euro and went up the bell tower, which provided us with a nice view, but considering I was 5 months pregnant at the time, it was no small task. The stairs going up were narrow and winding, and I found it dizzying on the way down. Everything looked the same and it felt like the stairs were never going to end. After seeing the Dom we went to a little cafe nearby. I don't remember its name, but it had delicious crepes and a cozy atmosphere, making it a lovely place to warm up on a cold day. We strolled around the plaza a little and then went to the train station to wait for Nate's folks. We browsed the shops there and then has some food before our trainride home (and Nate had some of the local beer).