Itinerary suggestions from Frankfurt

I’d look at the Rhine, Mosel, and Lahn River valleys. Lots of small towns and good scenery. Manz and Cologne are two larger cities with museums, etc.

I agree with stephen, basically. Stick with the Rhine Valley (between Bingen and Koblenz) and the Mosel Valley for cute towns and hiking.

The Mosel is better for easy/scenic/peaceful biking.

"Unique" places on the Mosel:

Wine underground by train to Traben-Trarbach: https://www.traben-trarbach.de/en/underground2.html

Cochem's Bundesbank Bunker: https://www.tripadvisor.com/Attraction_Review-g198637-d10195864-Reviews-or5-Bundesbank_Bunker_Cochem-Cochem_Rhineland_Palatinate.html

Beilstein - a 1-hr. cruise from Cochem: https://upload.wikimedia.org/wikipedia/commons/7/73/Beilstein_%28Mosel%29,_2012-08_CN-01.jpg

Burg Eltz: https://burg-eltz.de/en/homepage

Reichsburg Castle in Cochem - walk up from town or catch shuttle bus for a tour and the view, tours in English but pandemic-dependent:
https://www.youtube.com/watch?v=2FfYybdulNU

Klotten, near Cochem: the "Klotti" amusement park with animal exhibits and falconry show

"Unique" spots in the Rhine valley worth visiting/touring:

Marksburg Castle (Braubach)
Rheinfels Castle (St. Goar)
Chairlift in Boppard
Cable car lift in Rüdesheim
In-town sights in Rüdesheim
Remagen's WW II Peace Museum (NORTH of Koblenz on the route to Cologne)

Recommended river cruise segments...

Rhine: Rüdesheim or Bingen > St. Goar or Boppard
Mosel: 1) Traben-Trarbach > Bernkastel 2) Cochem > Beilstein

Aachen makes for a fine city to visit as a day trip from Cologne.

One idea is to spend a few days in Frankfurt. There's a lot to see there and nearby Mainz and Büdingen, perhaps Wiesbaden, are good day trips, all with a lot of historical interest.

"...worth stopping to see or stay north of Frankfurt....?"

I heartily suggest Marburg an der Lahn, a very historical and cultural place. I first saw this lovely town in Aug. 1977, well worth you time. The last time was in June 2007 after landing at FRA, took the train to stay a couple nights in Marburg before starting the trip.

I'm not sure what time of year you'll be there but it makes a big difference.

I will also be in Frankfurt—for 8 nights around Thanksgiving—and late November has its ups and downs. Many of the castles along the Rhine (and sadly Eltz Castle) are either closed, having extremely truncated hours, and usually no English-language tours. And it can be a bit too cold and rainy for hikes, with the sun setting early as well.

The flipside is this is the week the German Christmas markets start to come to life! The cities will be lit up beautifully, and the cold and dark mean more time for long meals and bars and theater.

This is how I am planning to break down my time, all by public transportation, if it helps give you ideas...

• Saturday - arrive, sightsee in Frankfurt
• Sunday - visit Bacharach, St. Goar and Castle Rheinfels, and maybe Koblenz (though Koblenz seems to be dead in late November)
• Monday - Frankfurt sightseeing in the morning; I work from my hotel at night
• Tuesday - Mainz sightseeing in the morning; I work from my hotel at night
• Wednesday - full day in Cologne including the Christmas market
• Thursday (Thanksgiving) - probably Marburg, or maybe a group day tour to Luxembourg, and Frankfurt at night
• Friday - Rothenburg ob der Tauber
• Saturday - Nuremberg
• Sunday - Last stroll through Frankfurt, then fly home

Not to hijack your thread, but definitely interested in any recommendations, advice, etc. that anyone has.

Truly appreciate all the suggestions! Thank you!!! (it's amazing to me how much info was shared in just 24 hours)

@Jeffrent - we'll be traveling in late October. I've visited several Swiss Christmas Markets and those were a special experience so I hope you're able to get to the ones on your itinerary.

Going to go do my research now. This is getting fun!

...we'll be traveling in late October.

Nice time to travel in Germany. Chilly, probably, with shorter daylight hours and more inclement weather - and Christmas is still way off - but "exploring cute villages" will be very doable, and crowds will generally be absent except for super-hyped destinations like Rothenburg. The days you've chosen to visit, if spent along the Rhine, will not be impacted by the closures that Jeffrent might experience in late November. Small towns like Bacharach, Oberwesel, and Braubach will not yet be shuttered. Marksburg Castle, probably the most prominent castle destination in the Middle Rhine Valley, is open year-round anyway.

Rheinfels Castle in St. Goar: Open daily 9-5. Even the shuttle from town is still scheduled to be in operation through Oct. 31. (Although Rheinfels is usually the main point of a St. Goar visit, even St. Goar's obscure little Bear-and-Puppet museum - which I've never been drawn to - appears to be open daily through December.)

CRUISES: Bingen-Rüdesheimer will be operating its Bingen > St. Goar "Loreley" cruises through Nov. 1. K-D cruises ends its regularly-scheduled cruises on Oct. 23 but may have a winter schedule in place for later dates.

Through October, most other highlights should be accessible as well... some examples...

Burg Eltz: open through Nov. 1
Remagen WW II museum: open 10-5 daily through Nov. 15
Boppard's Chairlift: open through Oct. 31