.....and what's reddit got on offer, dazzlenation?...well, i'm not entirely sure why i picked up on 'this one' but anyway....go figure:

https://www.reddit.com/r/interestingasfuck/comments/1omaccr/this_castle_in_graz_austria_has_a_double/

https://mary2point5.tumblr.com/

https://www.graztourismus.at/en/sightseeing-culture/sights/burg-double-spiral-staircase_shg_1444

st agydius, anybody?

https://en.wikipedia.org/wiki/Aegidius