Must see train route in Central Europe.

Greg,
The Bernina Express has views of Glaciers, so snow guaranteed.
The Glacier Express no longer has, since it was diverted through the Furka Tunnel. The old Furka route has been taken over by a steam 'museum railway', but they only run from June.
Timetable here: https://www.dfb.ch/fileadmin/shared/dfb/marketing/PDF_Moser/2016/dfb_fahrplan_preise_2016_deutsch_web.pdf
Main website here: https://www.dfb.ch
Practically any route in Switzerland is nice.
Take the main route from Austria to Switzerland (Innsbruck - Feldberg - Buchs). This is longitudinally through the Alps.
From Köln (Cologne) to Frankfurt the ICE high speed trains blast along the new High Speed line, try to take the "old" route through the Rhine Valley.
The Badische Schwarzwaldbahn (Black Forest Line) from Offenburg to Singen is also worth it.

The Glacier Express in mid-January is spectacular on a clear day, as is the Bernina Express. Switzerland can't be beat for "in-your-face" spectacular vistas. But for lower key beauty, Franconia (Northern Bavaria) and Thuringia, especially on local branch lines, are up there.

Switzerland (though expensive) has marvelous train routes. The Gotthard line was the wonder of its age when it opened in 1882, with loop-the-loops, zigzags, and spiral tunnels. I think it's most dramatic southbound: Arth-Goldau, Göschenen, Airolo, Biasca. The Brünig line (Interlaken to Luzern) and the Bernina line (regular trains as enjoyable as the named expresses) go over mountains as well, and they're both narrow gauge to boot. In Germany, along the Rhine is beautiful (roughly between Mainz and Koblenz). The east (right) bank gets only local trains now but it has more views of the river. Enjoy your trip!

Thanks for your advise!!! Is the Semmering line in Austria a beautiful trip and worth the extra mileage? If I have a railpass, do I have to pay for all trains between Disentis and Zermatt? Is Brig to Spiez covered by railpass? Are they worth it to pay extra?