10 day itinerary suggestions

What are you interested in? Historical museums (what periods)? Art museums (what periods)? Archaeological museums? Ethnographic museums? Historical sites (what periods?) Beautiful scenery (what kind)? Hiking? Architecture (what period?) NIghtlife?

Responding to acraven's question is a first step.

Also, you say,

"I have seen and am abundantly familiar with Bonn, Cologne, and Munich and not interested in these areas (will have stayed in Cologne the week prior)."

It's not very clear to me whether you mean these specific CITIES, or if not, what you mean by "AREAS." There are lots of destinations not far from Cologne/Bonn that you might not have visited during your Cologne week and might be worth visiting since you're starting out from there anyway...

Aachen
Monschau (gorgeous town near Belgian border)
Münsterland 1 (very different from Cologne/Bonn; quiet rural area + the university city of Münster)
Münsterland 2
Trier, Cochem, Bernkastel and the rest of the Mosel Valley
Middle Rhine Valley (between Koblenz and Bingen.) Think old-world towns,wine, castles, scenic train rides and river cruises. It could be logical to visit the MRV at the END of your trip if you're flying out of FRA.

Thanks for the responses. Sorry for the confusion and will try to answer as best I can.

I have been to those cities (Amsterdam, Bonn, Cologne, Munich) several times but not necessarily familiar with surrounding areas. Additionally, we did do a trip to Salzburg/Hallstatt and explored nearby areas several years ago.

I am interested in art museums much more than historical. Some interest in historical museums and sites. Periods not important. Quite a lot of interest in architecture and beautiful natural scenery and enjoy hiking. No interest in nightlife. My traveling has always been less about historical museums and more about the scenery, food, architecture, and some occcasional art.

One of the things that is making this difficult is my wife is not traveling and so no other input to narrow the choices. There is obviously lots to choose from in Germany? Baltics? East? South? Bavaria? Nobody can make a wrong suggestion but just looking for other perspectives from experienced travelers.

The Rhine and Mosel Valleys are both great outdoor venues - I've enjoyed a lot of hiking and some biking there - and both feature great old-world architecture.

Sounds to me like Bruges + Ghent + whatever suits you from the list of German destinations I suggested might combine well. Cologne > Ghent takes around 2.5 hrs; Koblenz (rail hub for the Rhine/Mosel region) is about 4 hours from Ghent. So you wouldn't be wasting much travel time and money with this combination, which to me sounds just about right for 10 days.

Don't forget our beautiful north! Hamburg, Lüneburger Heide, St. Peter-Ording, Schwerin . . . .

Thanks for the suggestions.

Leaning towards Belgium and then working my way down to Frankfurt. Does seem to make the most sense and wastes the least amount time in my situation.

I had never even thought of Muensterland…lots of interesting places in Germany.

I am intrigued by northern Germany…Schwerin, Lubeck, Wismar, and even Stralsund/Rugen but perhaps for another trip.

If you want art museums, then do plan on spending some time in Frankfurt. The Städel, the Schirn, the Modern Art Museum are all excellent. Check their websites to see what exhibitions are being featured when you are here. For natural beauty, head over to the Palmengarten and the neighboring Botanical Garden. The City Forest which is between the airport and the city on the Sachsenhausen side of Frankfurt, is 11,000 acres of trails and lakes. It may sound odd, but the main cemetery is gorgeous and well worth a visit. If medieval churches are of interest or their artwork, stop by the Karmeliter Cloister to see the wall paintings of Jörg Ratgeb, or the Justinus Church in Frankfurt Höchst, or the Deutsche Ordens church in Sachsenhausen.

Great museums in Berlin of course.

And hiking in the Harz for moderately high mountains, or Mecklenburg-Vorpommern for a totally flat lakes area. Both beautiful in their own way.