I don't think anyone has started a threat like this before, but here's a place to discuss mines which are in some way very unique, by working methods, situation, how they first came about etc.
Here is my list:
The Blands Coal Mine, Lancashire: small coal mine apparently opened up from a trapdoor in the cellar of a farm house in around the 1770s, a narrow seam of shallow coal was mined beneath the house and into the garden, later converted to a cellar. The tunnels were rumoured to link onto the nearby Clintsfield colliery but I don't think that's likely.
Parisian catacombs: can't say I know much about them, but in and around Paris limestone and I think gypsum were quarried underground, some of these workings are quite old and beneath elevated areas of Paris the mines go quite deep. They are deeper than the Parisian métro system and many were used I think in the 17-1800s and earlier for the plaster of Paris industry. Some of them were also used as cript space for Notre Dame and presumably other churches when room ran out in the churches' cripts. The mines or catacombs are a popular site for exploration although apparently illegal in Paris, the mines are so extensive that a lot do it, many of them are home to graffiti and other artwork which has taken considerable time to complete.
more later
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