A "Mark Twain Room" is in the Griechenbeisl (restaurant), Vienna, where
he, among many another celebrity, put his autograph on the ceiling: 
https://www.griechenbeisl.at/our-story/
Another curio of potential interst to the forum is the bronze statue of
Twain seated on a park bench in Lüneburg and the history of how it got
to be there:
https://www.landeszeitung.de/lokales/lueneburg-lk/twain-legt-in-lueneburg-an-AK5Q6UVMLYVH4EXNDGULU35UQX.html

Happy Trails!

Winston