2 night stopover between Amsterdam and Strausbourg, France.

Carole - You can rover over to the town of Rüdesheim am Rhein Germany and make a stop in your journey to Strasbourg for the 2 nights break up. You will have the opportunity to relax, tour the Medieval Brömserburg Castle and wine museum there, wine sampling along the Rhine, and visit an automated musical instruments museum.

Bon voyage!

I'm a huge fan of Cologne, which can't be fully seen in one day. Because it's counter-intuitive, I want to mention the surprising Google Maps "advice" to start with Thalys to PARIS! It look like similar rail hours, and you don't care about the station change if you sleep a night in Paris. Thalys is much cheaper with non-changeable advance purchase.

A word on Rüdesheim am Rhein... you'll read on this website that it's too touristy (echoing the opinion of the Mr. Steves, but ignoring how touristy many other locations he recommends can be). But I find that Rüdesheim is really fun at night. Many of the restaurants feature live music. The genre, Schlager, may not be to everyone's taste, but you see lots of young people (quite frequently in bachelor and bachelorette parties) from the surrounding larger cities bar-hopping and generally having a good time. This is a great example of that "experiencing local culture" thing that posters here claim they want to do, but don't often attempt.

I would check where the fast trains go and select a stop on the route

Rüdesheim is just one of several possible base towns that lie in the Upper Middle Rhine Valley (Germany's "Castle Country" and a UNESCO World Heritage site.) Besides "castles", think old-world towns, half-timbered buildings, great scenery, wineries and vineyards, river cruises, and outdoor activities...

https://www.germany.travel/en/towns-cities-culture/unesco-world-heritage/upper-middle-rhine-valley.html

Castles: http://www.loreley-info.com/eng/rhein-rhine/castles.php

Map showing all the towns, railways and ferry crossings: http://www.loreley-info.com/eng/rhein-rhine/walking-hiking.php

Koblenz is a mostly modern town that lacks the atmosphere you will find in the smaller towns like Boppard, Oberwesel, Bacharach, St. Goar, and Rüdesheim (the one town that routinely gets overwhelmed with visitors on tour buses.) If this area interests you... I say stay right there if you want to tour some castles and explore these towns. I would normally suggest St. Goar as an overnight or two-night stop - very convenient for train users due to its central location and good ferry crossing, and probably the most scenic spot on the whole river. St. Goar has an adequate number of restaurants and several hotels with direct views of the river and the opposite river bank (have a look at Hotel Rheinfels and the Rheinhotel St. Goar for starters.)

https://upload.wikimedia.org/wikipedia/commons/e/e6/Sankt_Goarshausen_Burg_Katz_2012.jpg