In the beginning of January I will be visiting Vienna, Bavarian Alps near Salzburg, and Prague. I would like to visit a therme pool that will let me be outside in the winter. From Steve's guide the Royal Crystal Baths are what I am looking for. Are there any others therme pools like that in the areas I am visiting? Does the Konigliche Kristall-Therme let people use there outdoor pools in the winter?
Check out the Watzmann Spa in Berchtesgaden.
There are several thermal pools in Karlovy Vary. Only slight detour when going to Prague from Bavaria. For more information google thermal pool in Karlovy Vary.
Check information on the Felsentherme in Bad Gastein, Austria. Following a morning hike up the mountain, an afternoon visit to the therme soothed our weary muscles. Lying in the warm waters looking up to the snow-capped mountains is a wonderful memory!....as is sitting on the therme's cafe balcony in warm robes sipping a beer!
I hope you have a chance to visit a bath. My friends and I spent an afternoon at the Royal Crystal Baths in May and it was a highlight of our trip. We progressed from pool to pool and ended up outside looking up at the Neuschwanstein castle and the snow covered mountains. What a great break from all the sightseeing!