Since you will be in Stuttgart and the Black Forest area, don't miss a chance to chill out in one of the spas of Baden Baden. Many Europeans love to vacation there and it is a neat town to walk around in filled with cafes and not to expensive restaurants. The spas are very elegant and will be a nice rest for you and not prohibitively expensive (bathing suits optional!) Afterall, President Obama stopped there, so how bad can it be? It is also a fun drive as the road twists and winds up the mountain to get there.

the train ride from Tubingen to SIgmaringen is very scenic

Here is a nice city guide for Frankfurt and the surrounding area with some of the highlights and events going on for the next few months (you did not give a time frame from when you will be here). It is fairly comprehensive, with some good photos too. Frankfurt is a good base city for various side trips. There are so many great little towns nearby that are easily reached by train or S-bahn.

http://frankfurt-on-foot-cityguide.blogspot.com/

you can travel together very inexpensively within a given state. I believe when we were there it was approx. $20 Euros for a family day pass of unlimited travel.>

I believe they cost 29 euros to 39 euros now for these Lander Tickets - you cannot use them on express trains but they do cover all other forms of transport from trams to buses to metros to regional and commuter trains.

If you buy a German Railpass then extra days after the minimum is only about $20/day so however - but as up to five can ride on the Lander Ticket i think the more traveling together the cheaper the Lander Tickets are p.p.

All Lander tickets are covered on www.bahn.de - German Rail web site.

remagen: I went sept. 2007 The drive from the mosel wasn't bad,but i sure would not return.Not much to see and the museum is full with 6 people. just my take jayvee

321sister - i have not gone in the Remagen Bridge museum and yes would only take a look at the remains of the bridge if passing by it between Cologne and Koblenz. It's a sight that is more evocative of its historical importance than the scant remains itself.

palenque; buy a post card. jayvee

Not sure if you are still planning to visit Stuttgart or not, but here's my two cents. Although I spent 2+ years living in Stuttgart and loved every minute, it doesn't make a whole lot of sense to split your visit between Tuebingen and Stuttgart. You could stay in Tuebingen for the whole time and take a day trip into Stuttgart and visit the Mercedes-Benz museum (if that's your cup of tea - it is fascinating!). There also aren't a whole lot of budget hotels in downtown Stuttgart.

There are many wonderful towns to visit in the vicinity of Stuttgart - Ludwigsburg with its gorgeous Residenzschloss has been mentioned (English tours available, but check the times in advance); another favorite that I believe you can get to easily by train is Schwaebisch Hall (smaller than Tuebingen).

For a lovely hotel in Frankfurt, I found this one in Sachsenhausen. http://www.hotel-am-berg-ffm.de/

This one in Westend: http://www.hotel-goelz.de/

and this one in Bornheim on the Berger Strasse, and it sits across from 2 great half-timbered Applewine garden restaurants that were built in 1600. http://www.bornheimer-hof.de/

Lucky you - 3 weeks in Germany!

You may have moved on from this question, but I loved seeing the Charlemagne-built church in Aachen, and the surrounding old part of the city. The cathedral museum was also worthwhile. It's not far from Cologne, so a day hop will suffice. Cologne's cathedral is simply stunning, and the Romanesque churches in the city are also fascinating. But then I love visiting old churches...

I think you are wise to save Berlin. When you do go, plan on a minimum of 4 days. Fantastic city!

I have not moved on from this question. I am so thrilled by all the responses - truly amazing- keep them coming.

Thanks

one more question - is there a luggage room at the Heidelberg train station ? If so we could visit Heidelberg on our way to Frankfurt from Koblenz.

There are lockers at the train station in Heidelberg.

I hope you are aware that Heidelberg is not on the way from Koblenz to Frankfurt but requires a detour. Heidelberg is however right on the way from Frankfurt to Stuttgart/Tübingen.