The day Paris caved in

This post is dedicated with admiration and gratitude to my friend Gilles Thomas, for his knowledge of Paris’ history — and for his generosity in sharing it.

Paris’ history is full of unsung heroes whose names have largely been forgotten. One of these is Charles-Axel Guillaumot.

Charles-Axel Guillaumot
Charles-Axel Guillaumot, “the man who saved Paris.”

Esteban and I had the privilege of walking in Guillaumot’s footsteps about a month ago, when our friend Gilles led us on a tour of the Cochin quarry (under the Cochin hospital, in the 14th arrondissement).

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The Cochin quarry is not far from the official catacombs. But it’s a lot harder to get into: On this Saturday our little group followed Gilles into the hospital, past an underground garage, and through an unmarked door to reach the entrance.

Behind the door was a classroom of all things underground, with maps of tunnels and photographs of the men who dug them. Gilles described the “squirrel wheels” that were used to bring huge chunks of stone to the surface — and the voids those stones left behind.


Sometimes those voids would collapse, Gilles explained, and anything on the surface would fall into them. This happened in 1776 — one week before Christmas — when a quarter-mile-long trench opened on the Rue d’Enfer and swallowed an entire block of houses.

Fearing more collapses, the young King Louis XVI appointed our hero Charles-Axel Guillaumot to be the first Inspector General of the quarries. But ironically, because of bureaucratic delays, Guillaumot didn’t actually start work until April 24, 1777 — the date of the next major cave-in.

A descent into the past

Our heads filled with visions of calamity and collapses, we marched single-file past Guillaumot’s portrait and down a long concrete stairway.

Several of Jérôme Mesnager’s exuberant “white bodies” adorned the walls — a stark contrast to the remnants of a 1930’s civil-defense shelter that greeted us when we reached the bottom. (Pardon the quality of the photos; I took them while walking.)

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Like the official catacombs, the Cochin quarries also serve as a museum (restored and operated by the S.E.A.D.A.C.C. association). But unlike the catacombs, the Cochin quarries are not generally open to the public — nor do they contain human remains.

I was anxious about how Esteban would react, because it was his first time underground. (He’s tall, and I worried he would feel claustrophobic from all the hunching.)

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But to my delight he seemed as fascinated as I was.

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Gilles showed us the tools the quarry workers had used to extract the stone, and one of the wells where they had drawn water to mix concrete.

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He also pointed out the markings. Some corresponded to the street names directly above our head. A few were made of soot from the quarrymen’s torches. Others were left by the inspectors, indicating their initials and the date of the inspection.

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In the footsteps of Guillaumot

Traces of Charles-Axel Guillaumot were everywhere. (The G in the inscriptions denoted his name, along with the pillar number and the date.)

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But traces of the king who hired him were harder to find. Once ubiquitous, now only 10 inscriptions of the royal fleur de lys survive. One was on display near the entrance; another was inaccessible due to flooding from the Seine.

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Every engraving had a date, but I saw none for 1789 — the year of the French revolution. That’s in part because Guillaumot was removed from his position and imprisoned due to his royal appointment. Fortunately, he was released in 1794 and given his job back.

There were also some traces of Antoine Dupont, a mathematician who preceded Guillaumot. Dupont built some 100 pillars in areas that showed signs of stress. Alas, the April 24 collapse proved the inadequacy of his efforts.

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That’s why Guillaumot decided to shore up the walls, too, in some especially vulnerable parts of the quarry.

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But in spite of his valiant efforts the ceilings continue to crack …

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… and in some cases, collapse. We passed one active cave-in that was slow enough to be considered stable, but that still motivated us to walk a bit faster.

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Esteban and I also hurried past this old patch, just in case.

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“Fontis” inscriptions indicated other cave-in sites — like this one, which has long since been reinforced.

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In a couple of other spots, we paused to survey the service wells the quarry workers used to bring down supplies. It wasn’t hard to imagine their soot-covered faces gazing at the pin-dot of light, maybe hoping for a better life or thinking about a loved one.

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Just as it wasn’t hard to imagine Charles-Axel Guillaumot standing in the same spot, inspecting his work.

He was still the Inspector General of the quarries when he died in 1807 — and it took nearly a century after his death to complete the work he had begun.

Guillaumot was buried in the Sainte-Marguerite cemetery, but was soon lost forever among the hundreds of graves that were transferred to the very catacombs he helped create. Within a few generations, only a handful of people remembered his name.

But he was never completely forgotten. In fact, on October 4, 2017 the city of Paris inaugurated the Esplanade Charles-Axel Guillaumot in his honor at the corner of the boulevard Saint-Jacques and the place Denfert-Rochereau.

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“He saved the capital from collapsing,” reads the plaque. But the epitaph Charles-Axel Guillaumot truly deserves is, “He saved Paris.”



“Le mal des carrières est celui de plusieurs siècles ; il ne peut donc pas être réparé dans un petit nombre d’années. Ni moi, ni mes coopérateurs n’en verront la fin. D’autres auront cet avantage ; mais j’ai lieu de croire que nous leur avons frayé la route, et qu’ils n’auront rien d’essentiel à changer au système que j’ai adopté.” — Mémoire sur les travaux ordonnés dans les carrières sous Paris, et plaines adjacentes; et exposé des opérations faites pour leur reparation, par C. A. Guillaumot

“The problem of the quarries goes back many centuries; it therefore can not be repaired in just a few years. Neither I nor my colleagues will see the end of it. Others will have the opportunity; but I have reason to believe that we have paved the way for them and that they will not need to make significant changes to the system I have adopted.” — Memoir on the ordered works in the quarries below Paris, by C. A. Guillaumot





    • It’s an aspect of Paris that is even many locals aren’t aware of! I’m fortunate to know the world’s authority on the topic, and grateful he lets me tag along on these adventures. And thank YOU for coming along too!

  1. Hello
    Under the hospital Cochin (not far from the catacombs), there is indeed an underground gallery long of nearly 1 kilometer … which is visited.
    Finally, there was an exceptional visit for the population about 1 year ago
    here :

    I think that via an association it is possible to visit it, unfortunately I have no more information

    • Yes, Yoshimi, you are right! The association’s website is and they provide occasional tours like the one mentioned in Le Parisien. If this aspect of Paris’ history interests you at all, I highly recommend a visit! Merci pour ta visite. 🙂

        • Yes, the stairs are a bit of a challenge. But if you ever decide to do this excursion anyway I’m sure the kind people at the SEADACC would let you take your time in going down and climbing back up. I promise you it would be worth it! But in the meantime I will be content to follow your marvelous photographic adventures above ground. 🙂

  2. What an amazing post, Heide! I feel like I had the privilege of accompanying your wise guide on this rare glimpse into Paris history below ground. Surely I will never see it in person as I, unlike Estaban, am highly claustrophobic! 😰 I did laugh at the phrase that he did not arrive right away ‘due to bureaucratic delays’ as it still rings very true today. And the photos are fabulous – especially the blurry ones, which seem to capture the eerie atmosphere perfectly.

    • I’m sorry to hear about the claustrophobia, Mel — but that makes me extra-happy you were able to tag along virtually. And isn’t it funny to know that even back then there were bureaucratic delays? Plus ça change, eh? As for the photos: Well, my inner perfectionist wishes the blurry ones were at least framed properly, but I was quite literally running down the stairs to keep up with my group. Gilles isn’t one to stand still for long. 😉 Anyway. Thank you so much for stopping by!

    • Thank you, J. P.! I am indeed fortunate to know Gilles — he’s the same fellow who took me to see the World War I shelters in the countryside, and the abandoned railway around Paris. He has boundless energy, and a brain like an encyclopedia!

  3. This is SO FLIPPING COOL!!!! Your pictures! The history! I loved reading this! The Cochin Quarry sounds like the kind of place, I would LOVE to visit. So. So cool.
    Yes I am in awe, because words fail me right now, except I loved this so much! ❤

    • Thank you, Kate! This is quite a compliment, coming from an adventurous traveler like yourself. I am SO GLAD you enjoyed it — and thank you for making my day with your sweet comment.

      • You are so sweet! I loved this! I want to look into the the next time I go to France. (I LOVE this kind of stuff!) Awe you are so welcome! You always make my day! ❤

        • If you’re really into this kind of stuff, please let me know before your next trip and I will be happy to put you in touch with friends who specialize in these “hidden faces” of Paris. ;D

  4. What an excursion you were on, Heide. I would feel very uncomfortable if I were to go there alone. An impressive labyrinth though and great pictures despite all the running and the hasty walk by the cracks in the wall 🙂

    • I would be *terrified* to venture into these tunnels alone, Hanna! It’s so easy to get lost or twist an ankle — and in some parts of the quarries there’s a second level you can fall into. Fortunately those risks were all but eliminated by my knowledgeable friend and guide. I’m so glad you (virtually) came along, too! Thank you for stopping by.

    • Thank you, Jim! Between the tight quarters and the dim light, it was pretty challenging — so I admit I was pleased (and kind of astounded) that so many of them turned out ok. It also helps to shoot in RAW, though, so you can really crank on those shadows. 🙂

  5. Fascinating post. I knew some of this but not in this detail. Thank you so much for capturing all of this on film. I am not sure I could do this as I could feel the walls closing in on me as I read so to you again I thank you xx

    • It’s true that those underground tunnels are definitely not for everyone — but I’m glad you were able to overcome the virtual claustrophobia and learn a bit about the history of this place. It’s just one tiny layer of Paris’ history, and a great example of why I keep going back. There’s always something new to learn and discover! Thank you so much for stopping by …

  6. The history and the photos to go with, so interesting! I was not aware of this history – love learning new things “)) Thank you for the intriguing journey and the ongoing celebration of human achievement.

  7. Great post. A bit scary to think of the pressure the city must put on the tunnels. It makes me wonder what would happen if everyone in Paris jumped up and down at the same time? 🙂 🙂

    • Oh, Marie … HAHAHAA! Thank you for starting my day with a huge smile. I admire your (slightly devious) creativity! But let’s hope this idea doesn’t catch on, because I’ve seen some of the “reinforcements” in the tunnels and I’m not sure anyone should be walking above them, let alone jumping. 🙂 Thanks so much for stopping by and for brightening my day! 😀

      • Paris is one of my favorite cities. I will now be worried when I go there that the ground could slip beneath my feet. I will walk softly. 🙂

        • Just stay out of the 4th, 5th, 6th, 11th, 14th, and 15th arrondissements and you’ll be fine. HA HA! All joking aside, the gentleman who led us on this tour is just one member of a team that specializes in monitoring and reinforcing the quarries. Some have even been completely filled in with concrete! So no worries about jumping with glee (as I do) when you buy that first baguette or see your favorite landmark. 😉

    • You might be surprised by how well you’d adapt to this space — it feels more like a series of rooms with long hallways than tunnels. As for bravery awards: I second your motion to give one to Esteban. One for every single day he has endured my harebrained ideas! 🙂 Thank you so much for stopping by …

    • Oh goodness … I hope it wasn’t *too* terrifying a post! Visiting with an expert like my friend Gilles takes the fear out of it, because I know he won’t get lost or lead me into any truly dangerous sections of the quarry. The only risk really is falling behind because of my compulsive photo-taking — which is how we ended up with those “happy accident” atmospheric photos! But thank you so much for your kind words. I really appreciate your stopping by!

  8. Oh snap! That’s a cool place but I would faint half way down the first set of stairs. So thanks for the tour. I find these underground mazes so fascinating but I’m extremely castrophobic. On a recent trip to Bath, England, I stood outside on the steps for the entire tour. Closed spaces make me panic. Isn’t the will power/man power of the past just mind blowing? I mean, shu, that’s a mazing that human hands have constructed this far below the asphalt and shops. History is sure lost quickly isn’t it. My aunt and I spent 6 months doing family history investigation. It’s slow but when you discover a simple date or even where someone homestead, we’d get exciting. Cool Stuff! x K

    • I’m so sorry claustrophobia kept you from seeing the crypts in Bath. 😦 Rest assured it’s very common, and a completely normal and useful survival skill — so at least you’re not alone. But yes, it really is amazing what human hands and minds can accomplish. In fact, my friend Gilles just sent me a link this morning to Paris’ very first sewer maps, which the city has put online. Sewers sound so unglamorous, but they’re a mind-blowing feat of engineering when you think about it. As for YOUR family history project: That sounds fascinating! Have you blogged about it? xxx

      • Sewer maps for such an old city as Paris? Hell yah, that’s fascinating 😀 I love history stories of city’s, people, events and houses. Have you planned your next underground adventure then? Now they just bury a giant plastic pipe underground…boring. Future civilizations will probably not be as interested :/

        I have blogged about family history a few times. Have a boo, it’s not a lot. We are a quiet, unassuming clan…LOL Unless you’re at the dinner table with my brothers, ha!

        • HAHA! I love the idea that future civilizations won’t be as interested in our plastic-pipe sewers. I suspect you’re right — between pop music, politics, and the internet I’m sure future generations will have plenty of other things to ponder, LOL.

          If you’re in the mood for some old-timey map goodness, here’s the link to those old Parisian sewer installations:

          And thank you SO MUCH for sharing the links about your family history. Your posts are beautifully written and illustrated. You’ve done a big service to your family by telling these stories so richly, and with so much love. Hats off to your unassuming clan and loud brothers! 😀


          • You’re cheer makes my day dear friend! Thank you so much. Thank you for the link too! I peeked at those maps and WOW, right? It kind of slays me to think about these big cities back then because Canada is such a new country. Especially out west here. Even as a kid, my own city was quaint and casual and I pretty much knew my way around. It’s grown so so much though. I hear names of communities and say, “where on earth is that” LOL. I live in one of the older communities in Edmonton. My house (and about 40 others) was built on property that operated a brick company back in the day. You can’t plant anything without digging up broken bits of brick everywhere. History is in my backyard LOL xx

          • How COOL that your house was build over an old brickyard! I would be giddy about finding bits of brick — literally the building blocks of Edmonton! — right in my own back yard. Though I suppose maybe it gets a bit old when you really just want to plant the tomatoes, eh? LOL. All joking aside, though, I know exactly what you mean about the relative “newness” and familiarity of your home city. I feel the same way about Minneapolis and St. Paul. They definitely both have their charms and rich history, but in no way do they compare to the incredible layers you’ll find in an ancient city like Paris. On the other hand, it’s much easier to find a parking spot in Minneapolis/St. Paul than in Paris … so I guess we have *that* going for us. 🙂 xx

  9. WOW! I had no idea there were such treasures under Paris. I would have trouble being there for very long but I would love to try to see it all. Thank you for an excellent tour.

    • I very much hope you’ll have the privilege of seeing at least a portion of this network of tunnels, if it’s something that even remotely interests you. I was worried my husband would last only a few minutes, but he was down there with me for three hours! It really is so fascinating that you kind of lost track of time. Thank you so much for stopping by and joining us for a virtual tour.

    • I admit some of the tunnels *were* pretty narrow, Trudi. But it was encouraging to see that neither my husband nor my friend Isabelle found it too oppressive. I think it’s because it’s so fascinating that you kind of forget where you are! In any case, thank you so much for joining me on this little adventure.

    • I’m so glad you found this informative, Emilio! Guillaumot was a remarkable person and deserves to be remembered. Thank you so much for stopping by!

    • I agree it’s a pity this bit of history is largely forgotten — but it’s better than completely forgotten, I suppose. Thank you for stopping by, JM!

    • How cool that you live nearby — it’s a lovely, lively area! Well … if you’re ever interested in seeing first-hand what lies beneath le trottoir, I know just the guy to show you. 🙂

  10. Oh my….. it’s always the same! I live hardly 30km away from the heart of Paris and had neither the first idea of this place nor ever heard of guided tours into the belly of those quarries. How fascinating that somebody from Minnesota has to tell me about them 🙂 🙂
    When I lived in Devon, UK (southwest of England, a beautiful, calm region), everybody came and visited us. THEY travelled the UK up and down, from east to west and backwards, THEY told us all the beauties and crazy things they saw and discovered, WE were there to live and work and we had no time to visit as they did. It was (and still is) so unjust…. (plays the violin and squeezes a tear from her eyes)! I’m fascinated by this story. The closest I ever experienced was a ‘day’ trip to natural caves in the Jura of Switzerland when I was between 14 and 15. It was wet, scary, very very low, we had to crawl, it was slippery, stalactites and stalagmites ‘hindered’ our crawling and when we finally discovered, high above us and away from our frontal-torches, I was ready to break out in tears. It was so unreal…..
    I think now I could, just about, do a tour without screaming with terror! But I might have nightmares again for weeks to come. However, how interesting!

    • Your violin-playing and tears are well-justified, Kiki! It really is unfair that it’s so difficult to enjoy our “home” cities because daily life gets in the way. That said, I’m still honored that I was able to show you something completely new about Paris! If you ever want to go see this for yourself I will be glad to ask Gilles when the next tour is scheduled. Or I suppose you could contact the SEADACC directly at

      In any case … I am sure you would enjoy it immensely and guarantee it would be 300% less scary than the adventure you had in Jura in your teens. 🙂

  11. Thank you for this fascinating reveal of Paris’ secret past. Actually I’m glad to know that places like this are spared from tourist hordes. Paris has many more secrets to be discovered I suspect.

    I didn’t make it to the catacombs but I did see Jerome Mesnager’s white bodies around Paris when I was there.

    PS If you know how I can visit the underground lake underneath Opera Garner, please let me know. I did an after hours tour there but sadly the lake wasn’t included on it.

    • I’m delighted you enjoyed this “off-road” adventure, Mr. Draco! And delighted also that you spotted some of Mr. Mesnager’s works around town. I had the privilege of meeting him a couple of years ago and found him to be as warm and open-hearted as his whimsical paintings would suggest. As for the lake under the Opéra Garnier: I don’t know off-hand how one can get there, but I do know a couple of folks who can probably find out. I will inquire the next time I chat with them and let you know!

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