Real-Life Dungeon Crawling

Under the town of Provins, about 100km from Paris, there's a super rad network of underground tunnels.
See, the French like to build on top of quarries. They tend to build the important shit first, like castles and walls and walled castles, using locally-quarried stone.

Smart!

Then they go "Oh, fuck, we need to build other things here now, like houses for normal people that aren't castles."

Anyway, this is why a lot of French towns have some kind of tunnel network under them, Paris has its catacombs, and Provins has its underground (souterrain, in French). Everyone knows about the Paris catacombs, though. They've been a pretty popular tourist attraction since the 1700s, when bones got moved out of Paris's giant death pits from the middle ages into the cool pre-existing spooky zone beneath the streets.

Provins's have been made into a tourist attraction as well, but for centuries they were much more than that. After a huge chunk of the town got built out over where the quarry tunnels were located, the spaces got used by townsfolk in lieu of formal cellars, which were impossible in some portions of the town due to the network of ridiculous tunnels that was there instead.

Anyway, visiting those tunnels was probably one of the neatest things I've ever done. Can you imagine living over a huge underground complex and having to deal with it to get to all the crap you could otherwise have in your basement? Even with modern lighting and a recently-refinished floor, it's hard enough to navigate the terrain in the tunnels today. It's also really cold.

As a bonus to hearing me ramble about underground stuff, here's an encounter table of disgruntled townsfolk going about their business in the local dungeon:

On a d4 roll:

1. Karl the Chandler: Selling discount lighting implements to anyone who wanders by. Is accompanied by his two sons, who look exactly like him but shorter and less greasy.
2. Bert the Mushroom Collector: Using his 2HD truffle-hunting pig, Darlene, to find only the finest medicinal mushrooms. Very smelly, but incredibly friendly. Offers the party vouchers at his market stand, which tends to be open when he feels like it.
3. d6 Child Adventurers. Will insist they're not in mortal peril. They know where the nearest source of treasure is but insist they're capable of nabbing it. They are most certainly not.
4. A lost merchant trying to find his underground warehouse. He just took two wrong turns, but no one knows that. He'll pay the party handsomely (1d6x100SP) to help him find his stuff and get it to market.