Four nights in Germany after Riverboat cruise

I would say that Lucerne is the obvious place to spend those days. If you had a little more time I would suggest the area of the Berner Oberland, in the Swiss Alps south of Interlaken. Maybe you could shave a day off the Munich/Octoberfest craziness and relax in the beauty of the Alps!

In the Munich area I would recommend a visit to Dachau. It is very well and respectfully done, to honor those who lost their lives there during Hitler's time.

We're planning a trip next year and my wife wants to do a river cruise (she was thinking Danube) and I want to visit Basel (where I spent the summer many years ago). A Rhine cruise that ends in Basel sounds like it might cover both our desires. Would love to know more about your experience.

For Basel to Munich with a one night stopover, I think I would stop over in Lindau, the island city on Bodensee. You could get to Lindau either via Zürich and around the end of the lake at Bregenz, or, my preference, go through the southern Black Forest to Singen, then along the Bodensee to Lindau. From Lindau, Munich is less than three hours by ALX (a regional train, so you can use a 28€ Bayern-Ticket for two.

As for a Rhein cruise ending in Basel, I haven't gone by boat from Mainz to Basel, but I have been along most of that stretch of the river by car and by train. I didn't think that part of the river was that interesting - mostly flat - not like the Rhein gorge between Koblenz and Bingen.

You could get to Lindau either via Zürich and around the end of the lake at Bregenz, or, my preference, go through the southern Black Forest to Singen, then along the Bodensee to Lindau. <

Or you could go from Zürich to Konstanz, then do an nice mini cruise by switching to the katamaran ferry over to Friedrichshafen (Zeppelin museum) and from there go the last 40km or so to Lindau by train.

http://en.der-katamaran.de/ (timetables for summer aren't up yet).

I give great weight to any suggestion by Lee. You didn't say "by train", but I think that's what you meant. Advice could be different with a car (rent in Weil am Rhein to avoid foreign drop off charge.) I think October is too late to make the most of Lake Lucerne. If you still want mountains, Innsbruck is more practical. Don't dismiss Zurich. It's another hour, but I'd also look into Salzburg. You don't need another timbered town after a river cruise. Some larger city you can't see all of on foot in two days is appropriate.