Has anyone entered the Paris and/or Roman catacombs?

Preferably deep inside, beyond what is normally open to the public. Is it true that the deeper you go, the colder it gets? That’s what a friend who visited the one in Rome says (also what JK Rawling wrote about the Gringotts vaults.) I was an underground mine geologist for several years and I know that the deeper you go, the hotter it’s supposed to get. That’s what ventilation engineers are for.

We might also ask engineers exactly why it gets hot in the mines the deeper one gets.

Normally and in general, at a certain level below ground, temperatures tend to become stable and rather cool. I guess that you know what you’re saying about mines, but then it might be because they’re much deeper than natural caves (or mines/quarries close to the surface, as the Paris catacombes are for the largest part).

I’ve known some “cataphiles” (people venturing in the non-public part of Paris catacombs) and it’s the first time I hear a reference to the temperature becoming colder the lower you go. However, if true, it might be simply because the parts closest to the surface have a lot of exchange by a variety of conducts with outside air hence are closer to surface temperatures, while the deepest part are more insulated from outside temperature variations hence more similar in temperature level to regular natural caves, which might appear unusually cool to someone with no spelunking experience.

I was in some Roman catacombs this summer and it was chilly as soon as you got underground. We were mainly at the same depth the entire trip so I can’t answer your question. The guide didn’t mention anything about it getting colder if you go deeper, just that it was pretty constant temp year round.

Cold is always relative. I was in the Paris “catacombs” about 10 years ago. Since it was about 30C outside (about 85F) the less-than-room temperature walk through the boneyard was fairly cool. Occasional dripping water evaporating probably added to the coolness.

Not really Catacombs - in the centuries before heavy equipment, it was cheaper to mine blocks of limestone for the buildings like the Louvre, rather than remove 30-plus feet of overburden to create an open pit. This left giant galleries under the area south of Paris that became an ideal deposit site for emptying the overflowing church graveyards now inside the expanding city. After the revolution when the church had no influence, the revolutionary government took on the task of emptying the old bones from all the graveyards.

Same effect with the Roman Catacombs. I went into one southwest of Rome (Via Appia Antica at St. Stephens(?) IIRC? It wasn’t particularly cold, but cool temperatures contrast with summer heat outside and the high humidity seeping in from outside also makes the cold more easily felt.

Alas, I’m an armchair traveler. In Rome, at least, it appears that the less-known subterranean city is not necessarily deeper–just more extensive. This 1997 article in *Atlantic *gives some tantalizing hints.

Some of the links in the article have expired. But there is now a tour company called Roma Sotterranea.

(Wasn’t there a recent thread posted by somebody planning a Rome visit in July? It will be hot in the streets–but not beneath them.)

We were there in late June last year, and the catacombs were a welcome relief from the heat.

When people say “deeper” is colder, are they speaking of a lower elevation or simply farther from the entrance but on the same level?

It’s a good bet most folks repeating this factoid, especially those full of woo, have never considered the two different interpretations.

The whole of ancient Rome is hollowed out. The ancient sewers are inter-digitated with the ancient water mains, and between and around them the ground is hollowed out as the source of building stone and Roman Cement, with which Roman ruins and aquaducts are glued together, and the source material of Roman Concrete. The building stone was special too: it’s soft when mined, but hardens on exposure to air.

All done by slave labour, and the underground furnaces of the Roman Baths must have resembled popular conceptions of hell.

I’ve been in the public section of the Paris catacombs, which is about a mile long and fairly deep underground (20 meters - there lots of steps down at the beginning, and back up at the end) - temperature was comfortably cool, maybe around 60F.

I’m another who has been on the guided tour of the Roman catacombs. I agree with the other folks who have been. I wouldn’t want to go down there without a guide, however. I’ve also been in the underground part of Seattle, upon which modern Seattle is built.

I believe that the temperature of near-surface underground areas is the mean average of all the annual temperatures over the year, including both summer & winter*. SO it would tend to be cooler in summertime, and warmer than winter storms.

There is a point where internal heat from the earths’ core will warm up the undergrounds space, but I think that is deeper than these catacombs go. The Soudan mine, here in northern Minnesota, is over 2000 feet (600 m) deep, and stays at 51 degrees F (11 degrees C) year-round.

*That’s one reason houses in northern climates have basements.

I used to do a lot of cave exploration. The earths temperature at say, 10’ below the surface stays at a constant 50-55 degrees. With air circulation it might get to 60 as described above. Only the deepest diamond and gold mines in Africa are deep enough for the temperature to increase.

What others said. I’ve been on a guided Catacombs tour, and I’ve been a tour guide and amateur explorer of the caves near my home town Maastricht.

Both those caves and the catacombes are technically not (natural)caves; they are man-made limestone mines. In maastricht, those mine corridors are empty. In Paris, 18’th century Parisians filled the corridors with stacked bones from the clean up of the overflowing cemetaries in Paris.

Limestone, a building material, is a remnant of prehistoric seas. Lime stone is found in horizontal layers, not that deep below the surface. Usually no deeper then 100 feet below the surface.

So the temperature in such a cave will be the general underground temperature: a constant 10 degrees Celcius, all year round. It will feel chilly and damp in summer, and chilly and warmish in winter. It will always feel damp, but you won’t see water dripping from limestone; the material is porous and acts like a groundwater sponge.

To feel warmth underground, you have to go much deeper. It starts to get hot around 6000 feet deep.

The Roman catacombs (the actual empire age Christian ones) were not really mines. They were originally as I understand because the Christian cult adhered to the Judean belief that a time of judgement was coming when all would be risen to be called to account before God. Thus, unlike the Romans, they preferred to be buried intact rather than cremated to ashes and scattered. As a result, they were running out of graveyard space around Rome; they dug grave tunnels to make extra room for bodies. When the emperors began harassing the cult, they then used the burial tunnels as a place to gather and worship also.

This is why the French store their wine and cheese in ‘caves’. These days ‘cave’ has become a generic name for any wine store, but they used to be literally caves.

Catacombs aren’t very deep, and not in areas with high geothermal gradients, so they just benefit from the shallow insulation effects and also likely other chill effects from being in the phreatic zone, This masks any geothermal component if they don’t get any noticeable counter-influence from the geothermal gradient. But in an active geothermal region, the geothermal influence would be found even in shallow systems.

Here’s a little readingon the subject. especially check out Fig 4.3.1

This is not true, you get noticeable temperature increase in even relatively shallow (a few hundred meters) mines. Like the_diego, I used to be a mine geologist - in those African gold mines, and I’ve been in lots of other types - lead, platinum, coal, copper…

As a rule of thumb, after 200m below surface, things start heating up by around 15–30°C/km in most areas that concern us (it’s* a lot *higher in volcanic/geothermal terranes) . So even a 300m deep mine is going to be 1-3 °C hotter than on surface.

Deepest I’ve been is ~3km, whith a rock surface temp of around 50° C, air temp was ~40° C (but cooled down to ~30° with AC). Our overalls were kept in a freezer.

Farther from the entrance. Even when it doesn’t go deep, the temperature in a cave is stable and cool.

“Cave”, in French, means “cellar”, not cave.