Every major city has tours in tunnels and are usually pretty cool. The one in Rome is good. The one in Turin is just amazing, shows how the Italians used the tunnels to defend against the French army.

> Every major city has tours in tunnels and are usually pretty cool

I agree. Edinburgh has some amazing ones under The Royal Mile.

The Paris ones used to be quite extensive but the comments here make me wonder if they have been shortened?

The catacombs in Lima gave me pause. The environment there is very dry and so decomposition is presumably slowed. There was a very distinctive smell.

Naples underground was really cool. Tour ended in a Greek/roman theater that was found in someone's basement.

Yeah, the one about the tunnels being dug under the Berlin way was absolutely astonishing.

An architect I knew in Paris once pointed out to me that everything that the entire built environment in Paris was quarried from the limestone beneath it; there's as much of the city below ground as there is above it.

Architect from Paris here. That’s right, except the mines didn’t cover all of Paris, they were originally outside and eventually built over. [1] The underground networks below Paris are actually said to be even more extensive than the streets and extend many stories deep. These networks are the result of a complex layering of quarries, catacombs, sewers, bunkers, undergound metro, and even waterways [2], large parts of which have been abandoned over time. No public map is available, who knows what else might be hiding there.

[1] https://en.wikipedia.org/wiki/Mines_of_Paris [2]https://commons.wikimedia.org/wiki/File:Le_Canal_Saint-Marti...

I DJ'ed a rave once in one of the off-limits sections of the quarries under the Right Bank (Auteil maybe?) Insane acoustics.

Absolutely. Here's a map of the catacombs of Paris overlaid on a real map of Paris.

https://i.imgur.com/6ywDpJX.jpeg

>The project is now in its third year and the team will produce the first preliminary findings before the end of the year. Charlier predicts the work will outlive his career.

Excited to see what will come from this study over the next years, this was my favorite place to see in Paris last year, and wasn't too hard to schedule the visit (I think I booked one or two days before). Some sections are closed, and I read the catacombs are not fully mapped. Wondering if they will find something or someone long thought to be lost down there.

Almost all of the catacombs is closed. The tourism portion is like a few hundred feet. I have a couple of interesting links for you from UNDERGROUND KONTROL

Here's a guided tour of the closed portion by a knowledgable enthusiast: https://youtu.be/O3ufzGxfW6Y

here's a short (20 min) French language mini-documentary about the pastime of people who go to the catacombs. https://youtu.be/nRISC0cJwMU

It documents a real project they undertook to uncover and infiltrate the location of the WWII Nazi bunker for the purposes of producing a Rave. The rave had electricity that they were able to secretly install by jack hammering through a meter thick concrete wall.

A realistic rendition is the film Catacombs (2007) As Above, So Below (2014) is also interesting but more fantastical.

For a real tour showcasing a few of the organized rooms: https://www.youtube.com/watch?v=6Q8Hw3XCwhs

A interesting aspect of the Catacombs is that some Parisians have dug their own tunnels and added various objects in the rooms.

To better appreciate the extent of these quarries (≈300km) here's a map of the catacombs overlaid on a real map of Paris.

https://i.imgur.com/6ywDpJX.jpeg

Way too low resolution to see anything there.

I wish someone would fund a lidar/3d scanning of the catacombs. I don't know if it would be plausible in any capacity but It sure would be cool.