Where else between Frankfurt/Rothenburg and Paris

You could stop in the Black Forest in Germany (e.g. Freiburg im Breisgau) and Alsace in France (towns like Colmar and Strasbourg). From Strasbourg, you can take the TGV train direct to Paris. I did this in reverse: flew into Paris, train to Strasbourg and Colmar (stayed in Colmar which is a little smaller, both are nice towns), bus + train to Freiburg, train (eventually) to Rothenburg ob der Tauber.

A stop in the Mosel Valley e.g. Cochem might be worth doing as well - not far from Frankfurt. It's all possible to do by train though you might need some detours to see all of these places I mentioned.

Strrasbourg is 1 3/4 hours from Paris by TGV.

architecture, history, science/technology, culture, sweets, and just walking around.

Strasbourg has all of that in spades.

Thanks Andrew and Sam. Sounds like Strasbourg is a good choice and it look stunning, exactly what we want.

I really enjoyed Strasbourg and recommend it as well. I stayed in Gengenbach (a jewel town in the Black Forest) but took a day trip to Strasbourg and really enjoyed it. You might want to consider doing the opposite and taking a day trip to Gengenbach while you're in the Alsace. It's on the main train line and is a very quick 30 minute ride from Strasbourg. The town is "chocolate box" pretty and there is a lot to see and do; like taking a gentle hike, walking through the Aldstadt, which has many charming half-timbered houses, stopping to have some decadent pastries at one of several Bäckeries in the area or just meandering and enjoying the beautiful views.

I visited both Strasbourg and Colmar - short visit, day trip to Strasbourg, overnight in Colmar. I liked Colmar a little better, though it is a bit more of a detour on the way to Paris I guess. Strasbourg seat of the European Parliament, and when it is in session lodgings can be expensive and hard to get. Strasbourg seems bigger than Colmar - it has trams more like a big city. Colmar has only buses - it feels like a smaller town (maybe it is) so more quaint.

Suzann, Google Wurzburg which is between Frankfurt and Rothenburg. It is not between Frankfurt and Paris, but lots to see and do. Perhaps fly into Frankfurt, go straight to Wurzburg for a couple of days to get over jet lag and then on to Rothenburg and Munich. Nothing wrong with Frankfurt (I lived close to there for a couple of years), and it does have an amazing old town, but it just isn't my cup of tea. Others really like it. To each his own I guess. Hope this helps rather than roils the water.

Thanks again for the great suggestions and recommendations, they are all great. All the towns look super charming. Also, thanks for the lodging tip, perhaps staying in Colmar is a better option.
@TC, I agree Frankfurt isn’t exciting. My husband grew up in a small town nearby, Butzbach and want to show the kids the town. We are only spending one night there.

Which ROUTING do you plan to use for reaching Paris? See the options below with sample travel schedule to provide an idea of the total travel time involved.

• The direct ICE train to Paris enters France via Saarbrücken (a stop in Germany.) 8:56 > 12:52 for example.

• The ECE + TGV combo has a layover in Karlsruhe and enters France via Strasbourg. 8:06 > 12:31, for example.

• There's also a routing via Cologne with a layover there. 11:26 > 16:05, for example. Aachen, Liege and Brussels are stops on this route as well. Cologne is just an hour from Frankfurt; you could spend 1-2 nights there, then visit Aachen or one of the other cities en route by stowing your bags in a luggage locker. This routing offers more options than the others, but your choice depends on which places interest you most. Cologne sounds like you... chocolate museum, Cologne cathedral, some WW II history at the Documentation Center. Aachen's Cathedral is outstanding too.