Yeah, it's a cool place. So few have ever heard of it. They have frozen waves and waterfalls and stuff...A lot of stairs, ice-covered slippery ones, but is cool AF. We have been to a lot of places and done some amazing things, many here in Australia too! Thinking back it's so difficult to think what might be a favourite. Impossible to call it.
Add this to your list...It's worth the effort. They have a salt mine nearby too, also worth the effort going in. They have underground lakes that we boated over. Also, Adolf Hitler's Eagles Nest is in the area. We went there, eerie, but so cool to visit. (I love history.)
I love history too, that would be so cool to see. You probably don't have to pick a favorite, this world has so many unique interesting things as amazing as the next. Salt mines would be cool too, I never seen one, I like all that weird stuff. Basically anywhere with mountains I would like to visit for sure.