Daytrips from Koln

AAchen is just a short train ride away. You could take an 8 am train to Bingen (1.5 hr) then ride one of the K-D boats down the Rhine Gorge. Get off at Koblenz, ride the aerial tram over the river to Festung Ehrenbreitstein for great views down to Koblenz. Ride back, check the Deutsche Ecke monument. Grab a cab to the train station and be back in Cologne by dinner time.
In Cologne, do not miss Papa Joes Bier Salon in the Alt Markt. Also walk across the HohenzollernBruecke (railway bridge from Hbf over the Rhine, I believe Photokina will be in the convention center at the other end) Lots of "Love Locks" on the chain link fence separating the walkway from the train tracks.

Thanks!!:)

For a mix of old and new, Aachen for the old (Charlemagne's cathedral) and Düsseldorf for the new.

Excellent suggestions above. I would go to Wuppertal to ride the Schwebebahn, the suspension railway, admittedly not to everyone's taste. For a long day trip you could go to Amsterdam. Nearly three hours by train, it would give you time to relax and write in your journal.

I'll third Aachen.

Aachen is a great suggestion. How about Brussels, if you are driving, 2 hours 15 minutes. You could also visit the "Atomium" on the outskirts of the city, quite interesting.

Hi, I agree with the suggestions here as day trips from Köln...Wuppertal, Aachen, Düsseldorf, Koblenz also depending on your radius. How about Bonn? After Aachen?

Something a little closer for a short trip: try Altenberg. It has a wonderful ex-monastery compound that is now a park and sightseeing location with a great audio guide and a tremendous amount to see and do. I found the story fascinating and it's very peaceful, great for picnicking. Or, there is a nice restaurant onsite or in the nearby town of Odenthal. We drove on our last visit, but I could help you with public transit if you are interested; there are lots of bus routes. The town is just 30-40 minutes from Köln. I would spend about three hours there, then head back into town for dinner.