Best stop between Salzburg and Vienna

The Wachau Region (the UNESCO World Heritage Site between Melk and Krems) is best explored as a day trip from Vienna because 1) you can go on a nice weather day, 2) it is a bit out of the way from the main Salzburg-Vienna train line and 3) to have luggage would be a literal drag as you really want to start in Melk and end in Krems.

Give yourself the extra day in Vienna and do a day trip one if your Vienna days. Not much else is interesting between Salzburg and Vienna except Steyr.

You did specify rail stopover, but we slept in Munich between those two Austrian cities.

...but we slept in Munich between those two Austrian cities.

Not very likely, as Munich is not on the route between Salzburg and Vienna.

If you also considering a city aside from the countryside and small towns, then I would suggest Linz, the province capital of Upper Austria. I went there the first time in 1977 as a day trip from Salzburg, mainly to see the ominous side of its history, sense the atmosphere, etc.

Since 2011 I've been there a few times, going always by train ; the Schloss has special exhibits in addition to its permanent one.

The house where Mozart lived is there, just a residence, not a museum, and the Nibelungen bridge is a historical site with a plaque along its side attesting to its historical importance in the immediate post-war years in connection with the Sudeten-Germans.

Close to the Zentrum is the large military memorial dedicated to Austrian victories since the 18th century, including those in WW1, eg., the big Gorlice-Tarnow offensive.

Fred-thank you. My son is studying in Linz this semester so he feels that he has seen most of the sites there, but I’m going to ask about the ones you mention. Appreciate the tips!

I found the Ars Electronica Center in Linz most interesting.
https://ars.electronica.art/center/en/

@ asbinzer ....You're welcome.

If your son is spending a semester in Linz, I am sure he has already walked all over the Zentrum. Aside from seeing the special exhibit offered in Schloss Linz, the view is worth it too.

If he is interested in history, the surrounding areas have some sobering sites in addition to the concentration camp. Linz itself has the WW1 and WW2 German military cemeteries. I've seen these poignant sites in Linz.

There is a memorial to the escape in 1945 undertaken by Russian POWs and who were tracked and killed by the Nazi authorities (the SS and the like) and abetted by the local population. The event is known by its horrific name, " die Hasenjagd "(hunting down rabbits) . The memorial is located along the side of a country road outside of Linz...I've seen it. There are others too, one on German POWs.

The churches in Linz are also revealing in their displaying of memorial plaques pertaining to dates important in Austrian history,,,,1848, 1859, 1866, and obviously 1914. ...just some tips should he be interested in tracking down esoteric history sites.

Loved Bad Gastein. Train goes to Vienna and it's a pretty area.

During one of our trips in that area, we stayed in Salzburg and then took the short bus ride to St. Gilgen to take the boat for a few nights in lovely St. Wolfgang. From there, we took the bus/train to stay overnight in Melk. We took a boat from Melk to Krems and then caught the train to Vienna. That area is pretty, so it would be nice for you to be able to see some of it.