The White Gold of Turda, Romania
holeinthedonut.com
holeinthedonut.com
There is also another salt mine even larger - Slanic Prahova, the echoes and volumes of space are amazing. Real life Mines of Moria:
https://www.youtube.com/results?search_query=carrieres+des+l...
There were also some actual gold mines that the same Romans were taking advantage of close-by, at Alburnus Maior (also visible on the map).
[1] https://en.wikipedia.org/wiki/Roman_Dacia#/media/File:Roman_...
As per the mountains, they are not that impenetrable, but you're of course correct, the easiest way was to come through Porolissum, through the North-West passage, the "mountains" there do not surpass 700-800 meters in height.
That's how the Magyars actually did it about 800 years after the Romans, i.e. they came through today's county of Salaj, where the old Porolissum used to be. If I'm not mistaken the name of Turda itself comes after a Magyar ruler/chieftain called Torda (a Turkic-like name itself, but that's another discussion).
[1] https://religioacademici.files.wordpress.com/2016/03/transte...
The Turda Salt Mine is a pretty interesting site, you should visit it. The whole area is pittoresque.
I'm not complaining, just find it funny.
It's pretty clear they meant "picturesque". Also, the only lower-case form of "english" is slang for spin on a billiard ball because "English" is almost always a proper noun, so it should be captialized. ;-]
[0] https://whc.unesco.org/en/list/32/
[1] https://visitworldheritage.com/en/eu/royal-salt-mines-in-wie...
(Cluj is a really nice and fun city to visit. Highly recommended.)
[0] https://roszak.pl/klimatyzacja-dla-kopalni-soli-wieliczka/