Pretty much the only museum open the day after Christmas was the armoury, which actually has the largest collection in all of Europe. It's huge--four floors, and the armour and weaponry gets more advanced with each floor. Our tour guide was hilarious and kept using bad German-to-English translations and saying things like, "In former days...", "Or so...". Guess you had to be there, but he was a gem. I think the armoury is one of my new favorite places in Graz.