Underground Shelters: “Whenever we had to dig, we dug, except in sandy soils.”

Laurent and Jérôme Triolet have been studying underground shelters for forty years. They have traveled to many countries to explore them: Spain, Turkey, Benin, and of course France, mainly the Center-West and South-West.

W hat was "a story of teenagers in search of mystery" has become a passion, the subject of numerous jointly written works and a website (www.mondesouterrain.fr). After "Monuments emerging from the shadows, underground refuges" (Errance, 2022), which was limited to France, Laurent Triolet, a natural sciences graduate, and his brother Jérôme, a doctor of chemistry, have published "Souterrains du monde" (1), a panorama of the most surprising cavities dug by man to hide. Meeting with Laurent Triolet.

Underground, underground refuge, what’s the difference?

They are both dug by man, but the underground refuge has a defense system and utilitarian facilities, with several rooms. It is necessary to be able to hide from looters or passing armies if necessary.

Why are underground refuges concentrated from the Loire to the Garonne? Is it linked to geology? To conflicts?

Geology is not an obstacle. Whenever it was necessary to dig, it was dug, except in sandy soils. There are cavities even in granite, in puddingstones with large pebbles. Rocks must be sufficiently soft and sufficiently resistant. So, yes, conflicts, the Hundred Years' War, for example, with the great rides like those of the Black Prince, or even rivalries between lords, religious conflicts. Underground refuges are concentrated in particular in Touraine, Poitou, Saintonge, and in the Southwest as far as the Toulouse region.

Particularly in Gironde and Dordogne.

More than 1,600 underground caves have been identified in France, including more than 700 proven underground refuges. Approximately a third are located in Dordogne, Gironde and Lot-et-Garonne, or more than 200. There are some near Saint-Émilion, in Entre-deux-Mers… and especially in Périgord. Thanks to Serge Avrilleau (2), 164 underground refuges and more than 60 cliff cluzeaux have been identified, which are both refuges and high-altitude lookout posts. Along the Vézère, they form a line of communication: sound or light signals allowed information to be sent from one to the other.

Is La Roque Saint-Christophe, in Dordogne, an example of this?

It's difficult to pinpoint because of the overlapping of cavities over the centuries. La Roque Saint-Christophe is a vast complex, a veritable troglodyte fort with cavities and other fortifications. But the line of communication identified along the Vézère extends that far.

When are they from?

In the West and Southwest, the oldest date from the ^10th century, the most recent from the ^16th . This concerns the whole of rural medieval society.

There appear to be few isolated excavations.

There's always something above ground: a castle, a church, an enclosed farm. There aren't any beneath the great royal fortresses, which were very well defended. In the Agenais region, we explored one located beneath a church; you enter it from the cemetery.

You mention underground villages in the North.

They look like duplicates of the village above. But their defensive system is far from being as sophisticated as those in Dordogne, for example, where the number of rooms is, however, smaller, six or eight, no more.

The construction of these cavities required great technical skill.

They were clearly dug under the direction of people who knew the art of war. There are rare texts describing the digging in northern France. In southern Quercy, the blade of the auger used for digging was found stuck in an unfinished ventilation hole.

The extraction shaft, once plugged, may contain ventilation holes made of flat stones or ceramic elements. Oxygen supply must have been an obsession, and the ventilation system could become a weak point in the event of smoke accumulation.

To build them, the rock must be excavated and then removed; it's a huge undertaking. We estimated the time required for the excavation alone at one or two years for the large tunnels in the north, and two to three months for the smaller ones, such as in Gironde or Dordogne.

We sometimes had to live there for several days. What were the facilities?

Defensive systems, whether active or passive, can be very complex: loopholes, traps, very narrow passages. For example, aiming holes after a bend trapped intruders who were greeted by gunfire. We also see grooves in the corridors that were used to install large doors. In Lugasson, in Gironde, attackers encountered a door and a trap shaft, and found themselves at the mercy of refugees, who could reach them through aiming holes. The arrangements can be quite elaborate: niches for lighting, silos for food, benches carved into the rock. Some, such as those in Limousin or Agenais, even have small sculpted decorations showing aesthetic concern.

Are there any all over the world?

They aren't found everywhere, but they exist on every continent. Disrelated human groups have responded in the same way to the same type of threat. In Cappadocia, the networks are very extensive, very complex, and fascinating. In Benin, their density is impressive; they open up around wells, in veritable well fields. They also exist in Germany and Austria, and are well documented.

Comparing with other countries helps us understand, because there are constants in operation. In Vietnam, the caves are shaped to the size of the designers: during their last war, the Americans, with their large build, could not venture into them, but the more slender Vietnamese moved around easily. The Spanish "cuevas" are similar to the cliff cluzeaux of the Dordogne, perched caves that are both refuges and lookout posts.

There are fears, fantasies.

In Touraine, we were looking for an underground passage mentioned in a publication on a private website. The owner pointed it out to us, admitting that she had been afraid to venture there since childhood. Once through a thicket of brambles, we found a simple, narrow cellar that had fueled fears for generations!

The underground shelters are not open to the public. Their locations remain secret.

They are mostly privately owned and remain secret. And the relative lack of interest they generate is linked to their raison d'être: they are designed not to be seen.

(1) Actes Sud, 29 euros. www.mondesouterrain.fr

(2) Serge Avrilleau is the author of “Cluzeaux and underground passages of Périgord” in six volumes (ed. PLB and Libro Liber).