I have a in mind a series of posts I would do on real-world places that are inspiring in some way or the other for D&D.

The Catacombes of Paris make for an easy choice to include. I’ve visited them once myself, only the small part open to public mind you, and it was fascinating! If only I could go around the corner past the cordon I said to myself repeatedly on the visit. Of course on the whole of the catacombes are much bigger than the tourists part (1,7km), with around 300 km of tunnels the sheer size of the place is hard to fathom.

Here’s two interesting related articles for your edification:

https://venturetheplanet.com/an-adventure-into-the-un-official-paris-catacombs-a-mecca-for-urban-exploration/

(excerpt from the above link) « Colorful graffiti lined the ancient limestone walls, giving the place an odd, almost medieval funhouse vibe. But as we descended deeper, the graffiti gradually disappeared, swallowed by darkness and silence. »

https://www.atlasobscura.com/articles/strange-maps-paris-catacombs

(excerpt from the above link) « The general public’s “discovery” of the underground network led the city of Paris to officially interdict all access by non-authorized persons. That decree dates back to 1955, but the “underground police” have an understanding with seasoned cataphiles. Their main targets are so-called tourists, who by their lack of knowledge expose themselves to risk of injuries or worse, and degrade their surroundings, often leaving loads of litter in their wake. »

Takeaways:

• What if the primary goal of a mission is mainly to map a confusing maze? Not kill monsters (even if there are), not even treasure-hunting, just mapping?
• XP for mapping! An amount for each squares? More for important discoveries.
• Accurate maps should be rare and greatly coveted by would-be explorers and their patrons.
• Underground mapping is actually really hard. There’s the fact that you don’t have any point of reference to evaluate distances. Worst still is the possibility of tunnels criss-crossing and some going beneath others.
• In most tunnels you’re lucky if the ceiling is 6′ high, forget about the 10′ D&D norm! Often you’d have to walk all hunched-like and sometimes you have to crawl… And beware the flash floods.
• Graffitis should feature prominently in well-traveled areas.
• There’s also something interesting to do with the concept of legality or lack therof of catacomb-going or dungeon-crawling where the dungeon is right beneath the city. The more accessible sections being patrolled by cops/guards could mean trouble for illegal exploration… Bribes or legal permits could be part of the game.

In this series so far:

• Uxmal: Pyramid of the magician