Traveling between Dachau and Amsterdam.

The first thing that comes to mind would be anywhere along the Mittelrhein, which is more or less the halfway point.

Marburg is a beautiful old university town where the old town more or less winds around a central hill, topped with a castle. Or if you wanted to stay in a well-preserved town, still surrounded by an old defensive wall (and NOT overrun with tour buses), look into Büdingen or Fritzlar. I don't know too much about lodgings options in either, but I know you can stay in a castle in Büdingen.

Thank you so very much. We will look the towns up right away!

Ian

Boppard is a charming old-world town on the Rhine River with lots of accommodations and dining choices You could fit in a medieval castle tour if you want:

https://www.bellevue-boppard.de/media/e93668da-125d-4355-b8c4-2b380d21c09f/vierseenblick-boppard.jpg?mw=1200
https://upload.wikimedia.org/wikipedia/commons/9/93/Cc_Freya_Boppard_Vert.jpg
http://schnuggel-elsje.de/upload/Bilder/IMG_0131.JPG
http://farm3.staticflickr.com/2769/4245012678_95c5c8b305_o.jpg
http://home.kpn.nl/JLKampen1961/alb/Rome/Pauze%20in%20Boppard.jpg
http://www.deutschlandgourmet.info/bilder/gross/5710-Restaurant-Weinhaus-Heilig-Grab-Boppard.jpg
https://upload.wikimedia.org/wikipedia/commons/9/97/Boppard_Weinhaus_R%C3%B6merburg.JPG
https://www.boppard-tourismus.de/index.php?article_id=45&clang=1
http://ext.pimg.tw/samlucky5711/1379089584-1923285561.jpg?v=1379089585
http://www.marksburg.de/en/

Thanks so much. We will check it out immediately!

Ian