Where to go during Christmas in Europe?

Hi guys!

I'll be going on a solo trip to Europe. Will arrive in Germany on Dec 2nd and will also visit Austria and Czech Republic and will stay until the 28th. I'm having a little bit of trouble trying to figure out where to go on December 24/25/26th to pass the holidays. I know that most of Europe simply closes during those days, so I'd appreciate any suggestions for places/cities in which you can simply walk around and still have a good time despite of shops/restaurants/touristic places being closed. My first thought was to travel up to Tromso and try to catch the Northern Lights, but I'll be in Prague on the 22nd and flights to Tromso from Prague are really expensive and tricky to book.

(I know that one of the possible solutions would be to just leave before everything closes, but due to some circumstances that are not really relevant, I'm only able to use my saved miles if the ticket date is December 28th onwards)