This is not related to OP, but it has to do with mines nonetheless! Here's a cool video from some guys that explore old abandoned mines in the United Kingdom. They're very interesting because of the way they were built. Obviously, they have a lot more water to deal with! Second, trees were scarce, so most tunnels were built out of bricks they made from the rock they mined.

So, you have these mines that can be as old as 1700s or 1970s that are made out of old intricate brick work, but filled with water and look spooky. It's hard to imagine working down in those by candle light in the 1700s...or even with electrical light much later. Scary stuff.

Anyway, here you go: https://youtu.be/hoDGI4KGJnY