There’s also https://en.wikipedia.org/wiki/Williamson_Tunnels
"restorative" "meditation" "self care" "reflection" "me time"
Or he's really into dwarf fortress.
Or he wants to relive Teenage Mutant Ninja Turtles.
Or he wants a secret hangout.
I've actually visited an old Victorian-era house that had "a tunnel" in the basement. It ran from the front of the basement, underground, to somewhere underneath the public street where it terminated in a half-cylinder chamber perpendicular to the tunnel. Everything was lined with bricks, solidly built. I was told it was used to store booze during prohibition but no one is really sure. Found this on youtube (https://youtu.be/nDTyz7ivgNk?t=78), that's the one.
it's not risky, it is a time-bomb that will bury him alive.
I get better photo ops though
"So what are you up to outside of work?" "I uh... dig a tunnel." "Right."
But tunnel digging. Now that's a subject where my knowledge is limited. Teach me!
I might have tons of questions about it, or I might take that as my cue to close out my tab and move on to somewhere else.
It's just that most of the relevant conversations surrounding these things were had decades ago with other hobbies, and many hobbies probably wouldn't have a prayer of actually passing muster if they were new today - Full contact football being a good example.
This issue of legality that you raise is a good one though, and likely the most relevant, unless this guy is going out into the desert to do this.
I'm in favor of majorly reducing all hobbies that have danger or inconvenience to others. If you can't play 110DB music in the streets at night, there's clearly a general precedent and consensus that your hobby is not anything special and has no right to be a public nuisance or environmental disaster.
It's usually terrible sound quality just to make it even worse.
1. It's risky.
2. The end product doesn't seem particularly useful if we set aside the mental/physical benefits. i.e.: it's done for it's own sake.
3. It's novel.
I would argue that 1 and 2 are attributes that a great number of hobbies share. Skiing, Mountain biking, football, kayaking, woodworking, sitting in a chair and playing video games all weekend. All these things carry some very specific and often non trivial risks to health or bodily harm over time.
Of course because these hobbies aren't novel, the benefits of the hobby are well understood. Our understanding of the risks and how to mitigate them are also quite a bit more understood.
It seems to me that the real 'problem' with this tunnel digging hobby is how novel it is. Which consequently leads to a lack of knowledge about what the risks and benefits may be.
Of course it's possible the poor guy is just dealing with a mental illness.