Staying in Cologne Germany - Day Trip Suggestions

It's around 3 hours each way to Trier and back.

What about Linz am Rhein, a very attractive old-world town with half-timbered buildings and the like? Nothing like Trier at all but it's only an hour south of Cologne. You can ferry over to Remagen - also a nice town with some riverfront cafes on the pretty Rhine promenade and an attractive old town center - and an interesting WW II museum on the south end of town. From there take the train back north.

Linz brochure: http://www.linz.de/pdf/Linz_Prospekt_2007.pdf
Remagen Bridge Museum: http://www.bruecke-remagen.de/

Trier is a bit too far. I'd suggest Aachen, which has similar ancient historical significance and a spa heritage.

If you book in advance 3 months to save money, you could even go to Brussels/Antwerp, probably +-35 Euros and just over two hours. I still have Dusseldorf on my list. Aachen is a very good day out, and nearby.

Edit: One small argument against Trier is that Cologne is particularly known for its Roman monuments. No, it's not the same as Trier, but for a rebuilt, postwar city, Cologne has quite a lot of important Roman relics, and an really important museum that includes mosaic floors and things that can't be left outdoors.

Love these suggestions thank you so much. Please keep them coming!

I know I have a different view of daytrips than most on here but, if I wanted to daytrip to another town that I really wanted to see, I wouldn't hesitate to do a train ride up to 3 hrs each way. I would leave my base town early (probably around 8 am) so I would get to my destination town before noon, find a nice place to have lunch and then sightsee until about 6-7pm and be back in my base town by 10pm. I've done it several times and was very glad I did. So, if you really want to see Trier, then go for it.

How many days are you going to spend just in Cologne?
Bonn and Düsseldorf are the closest and the most obvious choices.
When in Bonn, make sure you visit German National Museum of Contemporary History (Haus der Geschichte). Excellent museum and therefore time consuming.

My wife wanted to go to the Haribo outlet store in Bonn, but when she saw the TK Maxx store on the main square (German version of TJ Maxx), it became the highlight. Thankfully, there is also a beer garden on the square for non-shopping husbands.

Thank you for all the tips. We will be one week in Cologne. As I get you suggestions, I have been researching each location. Please keep the suggestions coming.

If you are interested in the ancient Roman heritage Germany has, Trier is a must-see. Even more than Cologne.
https://en.wikipedia.org/wiki/Trier#Main_sights

Charlemagne's chapel in Aachen is a must, too.

Thinking of visiting Aachen for sure like the chapel idea. Anyone ever been to a spa there?

Charlemagne's chapel in Aachen is going to be wonderful to see. The photos and videos look amazing. Thank you for this tip as well.

There is one English language tour per day. Be sure to get their early enough for a ticket.

Aachen for sure like the chapel idea. Anyone ever been to a spa there?

Not my favourite spa experience.

Plusses -

the source of the water is a spring right next to the spa, so the water is fresh, and it tastes very similar to the water at the free fountain at the TI near the cathedral.

It was pretty cheap.

It was ok.

Negatives -

A very old crowd, very few people in all.

Not much in the way of fun activities in the water like a current river, or bubble baths or jacuzzis.

Worst of all, the water is luke warm, nothing higher. I like a warm area from time to time.

Despite several trips to Aachen since, I've never returned to the spa there.

Thank you once again for all the suggestions. I am struggling with the on-line Germany rail website. Want to price out tickets for the day trips, but I can't seem to get the website to give me pricing this far in advance (traveling the first part of October 2016). Is there a way around this?

The website won't give you fares further in advance than the standard 92 days. Try picking today's date to see what the walk-up fare is, and a date three months in advance to see how big the advance discount is. The fares may possibly go up if there's a general fare rise between now and October, but it gives you an idea. Note that the discount fares require you to pick specific journey times in advance with no flexibility.

Also compare the return fare with the cost of a Nordrhein-Westfalen Ticket, which will give you unlimited travel for one day in the wider region that covers Koeln and Aachen for 29 euros for one person or 42 euros for two booked at the same time, and also includes local buses and trams. The limitation is that you cannot use long-distance express IC or ICE trains. If you tick the "local transport" box on the Bahn website search page it will show you only the trains you can travel on with this ticket. It also won't cover Trier, which is in the neighbouring Rheinland-Pfalz region.

BTW, there is a Birkenstocks outlet in nearby Bad Honnef.

P.S. Birkenstocks will pull out from Amazon.com due to counterfeits flooding the market.

http://www.cnbc.com/2016/07/20/birkenstock-quits-amazon-in-us-after-counterfeit-surge.html

Koblenz is an hour away by train. From there you could easily go to Braubach (Marksburg) or Moselkern (Burg Eltz) or even to Cochem (Reichsburg - not a real castle, like the other two). On the way from Cologne to Koblenz, you could stop in Königswinter to see Burg Drachenfels.

Again, I greatly appreciate all the tips. So far building an agenda around Aachen, Dusseldorf, Bonn, Bad Hannof, Burg Eltz, (yes, I am extending our time in the area)....

Question - Koblenz has been recommended. What would you suggest seeing there? Braubach? We are interested in sipping some local wines...Any suggestions?

I'm not sure what else there is to see in Koblenz other than the Deutsches Eck, but I did have lunch and sampled several wines when I was there. From Koblenz Hbf, there are buses and trains to The Marksburg (across the river in Braubach), which I would definitely recommend.

About Koblenz, just been in the area last week.
Deutsches Eck is a must see, and from there you can take a trip to Fortress Ehrenbreitstein ( second largest fortress in Europe ) with a cable car over the river Rhine. All done in about 3- 4 hours.
You might want to consider a short cruise on the river Rhine from Koblenz, they offer 1 hour trips and longer : http://www.koblenz-tourism.com/rhine/boat-tours.html

Ever thought about Andernach ( 1,5 hours from Cologne ), they have a cold water geyser: http://www.geysir-andernach.de/english/my_visit/

As for Burg Eltz- you need a car to get there or you need to book a tour. If you have a car there are gorgeous small towns along the river Mosel.

Düsseldorf, Bad Honnef and Bonn are NOT that interesting to be honest. Not much to see really. Just my opinion.
Much nicer is Limburg ( 1 hour from Cologne : old city center with half timbered houses and a cathedral ).
Essen ( 45 minutes by train ) is not a super a beautiful city, but has a a old coal mine which is an UNESCO World heritage site: http://www.zollverein.de/service/english-page

As for Trier, was there this spring for 5 days. I highly recommend it, outstanding roman buildings etc. and everything is in walking distance from the train station.

Fantastic post. Thank you so much for the tips and links! I will look into each.