Honeymoon in Germany

The Rhine is spectacular with some wonderful small towns. We enjoyed Bacharach, rheinfels castle in St. Goar, and a Rhine river cruise all easily accessible from Frankfurt. There is also the Mosel with Cochem etc...

If it were me, I'd fly into Munich, go to Garmisch-Partenkirchen (or somewhere around there), head west for the Bodensee (Lindau or thereabouts) and end up in the middle Rhine area, home from Frankfurt. Nothing original about these places, but popular for a reason, and easily doable by train. Others will have more specific suggestions, but 10 days is not a lot of time.

Although I prefer the Rhine, the Mosel is quieter and slightly less traffic-ed. (Posters here warn about river freight noise at some Rhine hotels.) We stayed at an EXPENSIVE but very romantic hotel, Weinromantik Hotel Richtershof, in Mulheim. But there are more options, and more to see without a car, in Bernkastel-Kues and Traben-Trarbach. Trier is not a "big" city, but it's worth more than one day, and high point of the Mosel. Don't forget this newsboard's religious devotion to Burg Eltz! One option you might consider is the busy Rhine, followed by a different boat to stay somewhere on the Mosel. Don't neglect to consider the train, because it is so fast and frequent, in comparison with the boat schedules. Use the search box here for "Middle Rhine" as a reference. Do you leisure-bicycle?

Alternatively, there are attractive places to base like Erfurt or Weimar, that are not "big" cities, but have enough to do for days that you don't want to take yet another train excursion. While German trains are superb, it's hard to do more than one town a day when you are using exclusively trains. Leipzig is much bigger, but does not for me (NYC native) have the air of a big city like Berlin. So it has lots to do, including daytrips to the magnificent Gartenreich Dessau Wörlitz (UNESCO WHS).

If you have the time, you could look at my 2017 comments about "Baltic Germany", but use the subheads to reduce the amount you need to read:
https://community.ricksteves.com/travel-forum/trip-reports/baltic-germany-fachwerke-landesgartenschau

This is not my specialty, but hiking is almost a religion in Germany, so even giant places like Frankfurt have access to out-of-town state and national parks for attractive countryside walks, some of them, like the Roman Limes, are UNESCO sites. I do think the best river access is Mosel/Rhine.

If mountain views are a priority, then I would fly in and out of Munich. I really love the Rhine/Mosel but there are nice rivers all over Germany. The Alps are best place for mountain views.

Regensburg and Passau have walkable old towns along the Danube with great histories. Landshut is an under-visited small town on the Isar River. All three are fairly reached from Munich and each other by train.

https://mcchelsea.smugmug.com/Other-2/April-2014-Landshut/

These towns are near enough to Munich for an easy train ride south to/from a second base near the Alps at Füssen, Mittenwald, Garmisch, Salzburg or ...

You could make it with two base towns. Regensburg or Landshut, and probably Garmisch would be my choices. The small town of Freising is our favorite for a last night in country.

Folks sometimes complain about Bavaria being so popular on this board. There is a reason. There is so much to see within 2-3 hours train rides from Munich.

My favorite Rhine village is Bacharach. It's very easy to get to by train on your day of arrival from the US. After a few days there I like to move on to Cochem, which is on the Mosel. Rent bikes from the KD place on the river and bike to Beilstein, which is my favorite village on the Mosel. I spend the day there, but then back to Cochem for the nights. You can tour Burg Eltz, which is a great castle on the Mosel. Lots to do in that area of Germany.

By the way, if you are a really "older couple", know that Germany and Austria both offer senior discounts at museums to people from all countries ( age 60 or 65 -- not sure which, since we were over both at the time.) Happy honeymoon!!

Another idea for water and mountains with good train connections would be to fly into Munich then head to Lindau on Lake Constance (Bodensee). After Lindau you can head up towards Frankfurt via the Rhine River or down to Lucerne, Switzerland and fly home from Zurich.

Picking up on Mona's suggestion, here's a plan of attack for you...

"...old world charm, rivers..."

Day 1: Train fron FRA airport to Boppard, lovely old-world town on the Rhine with great riverfront scenery and great base-town location for taking a Rhine river cruise and train outings along both the Rhine and Mosel River Valleys. Visit the Rhine destinations of Bacharach, Marksburg Castle in Braubach, Rheinfels Castle in St. Goar, Oberwesel, Rüdesheim, Remagen; on the Mosel, visit Cochem, Winningen, Burg Eltz castle (near Moselkern.)

"...mountain views..."

Day 5 or 6: Leave Boppard by train for Lindau on Lake Constance near the Austrian and Swiss borders. It's a 6+ hour train ride with a couple of changes of train (Ulm is roughly mid-way and a possible place for a mid-day stopover.)

Lindau tourist office site

Visit nearby Meersburg.
http://www.burg-meersburg.de/index_engl.html
https://cdn.pixabay.com/photo/2015/02/24/20/47/lake-constance-647824_960_720.jpg
http://www.burg-meersburg.de/index_engl.html

After Lindau spend a couple of nights in Switzerland and fly home out of Zurich.

Switzerland is outrageously tough on the travel budget but you will remember the mountain scenery much longer than you will remember what it cost to stay there. Lucerne makes sense.

I agree about the Mosel. I too have spent time in Traben-Trarbach. There are boat trips up and down the Mosel. In the fall (now), there are wine fests. These are best attended when you are not driving, as all would agree. I'd pick 2 locations - 1 on the Mosel, one near Munich. I'd spend 5 days in each, with side day-trips.

On of Germany's most beautiful hideaways is Schloss Elmau.
https://www.schloss-elmau.de/en/

• You will have some beautiful small villages around.
  
• Close to highest mountain Zugspitze: https://goo.gl/maps/5am5ibLemaw
• Close to famous and walkable river canyon Partnachklamm: https://goo.gl/maps/MWx8XUVYyxM2

Spend 5-6 days there with day trips, after that change over to Chiemsee and enjoy islands in that lake, and close towns of Salzburg, Rosenheim or Wasserburg. A day trip to famous Königssee is a must: https://goo.gl/maps/QndVZbf4TUw

Enjoy.

The Mosel area is very nice, but I would recommend Bavaria. Visit Rothenburg on the Tauber, Romantic Road, Munich and then down to Garmisch/Fussen. Go up to the top of the Zugspitze, tallest mountain in Germany.

I am so grateful for all of the suggestions, many of which have not shown up in my research! I can't wait to dig deeper into all of the recommended itineraries!