So, the Romans destroyed or reduced some mountains for mining. Consequences?
The local mountain god(s) are suddenly crippled and reduced, but not destroyed.
The local fata-faerie are unhoused, their territories laid waste.
Some ancient spirit is released, probably a dangerous one, or at least one that's unhappy at being rudely awakened.
And so on - local supernaturals are upset.
That was some time ago, though. Their vengeance is probably spent. What is the long-term aftermath?
Closer to the 13th C.: I imagine a mage who wanted to gather up all the mundane wealth of a mountain could use this sort of thing as a legal/moral defense. "The Romans did far worse than I!" I'm not sure that would fly at Tribunal, though, if some enraged mountain spirit caused harm to magi.
Any way, it's an interesting wrinkler for plots.
*and suddenly a pop-up suggests that my topic is similar to a bunch of topics that it is not in fact similar to. Go to sleep, web spirit, you're drunk.
The Romans had gods of everything; down to an individual god for each household and every different crossroad. They may have employed techniques (possibly now lost, probably Mercurian or Mecurian-adjacent) of placating the gods & spirits of places where ruina montium was used.
I'm not sure you can placate someone (including supernaturals) into letting their home be ruined, at least not in quantity. You'd have to dominate, compensate, transplant, reduce or restrain them. To use modern analogies, mining companies tend to do whatever is cheapest, usually domination.
The thing is that this mining technique did not actually destroy mountains, it just allowed for easier mining and likely was predecessor to other mining techniques like allowing water pumped into cracks to freeze overnight to break apart rocks. Certainly it would be far less effective than modern mining with dynamite, which also does not destroy mountains.
That's true: erasing a mountain is pretty hard and generally uneconomical. However, "cracking" a mountain to plunder its wealth does appear the stereotypical action that both weakens and deeply offends the local mountain spirit.
It also depends on what you mean by cracking. These were essentially mining techniques, they didn't open large rifts down the middle of the mountain, they didn't open up a mountain like an egg. They broke rocks up somewhat more effectively than previous techniques. So instead of taking a week to dig that tunnel into the mountain now it can be done in 5 days.
My key point here is that most of what we are talking about here is the hyperbole of ancient pitch men.
Anyway, if the ancient Romans marketer Pliney the Elder says they did it, in Mythic Europe they probably did.
So, to some extent or another the ancients used hydraulic pressure to reduce large areas of hills and/or mountains, possibly but not necessarily ranges of said above, and therefore it seems affected the local spirits in some fashion, which some storyguides might find an interesting basis for a plot.
That was the largest gold-mine in the Roman empire, worked by ~60000 laborers for 250 years. It was not the result of a single one-and-done event; so the actual Ruina Montium technique yielded much less spectacular results than simply glancing at the picture might lead one to believe.
There is also the distinct lack of a before picture. I mean the caption says it was the result of Ruina Montium, but without knowing what it looked like before we can't really know how big that impact was. I have been places that looked similar with no human hands being involved.
