If you want to know anything about what’s underneath Paris, you could try to find some cataphiles, people who spend time exploring the catacombs with flashlights and waders. But for the history, the man to talk to is Gilles Thomas.
A wiry, moustached man, Thomas works for the city of Paris, but he is passionate about what’s underneath it, both physically and historically.
The authorities, he says, are only interested in the structural soundness of what’s above ground - he's interested in preserving the history underneath.
The buildings of Paris were built out of the limestone and gypsum – or plaster of Paris – dug out of its belly. The Romans, who founded the city on the Ile de la Cité, found limestone along the riverbanks.
“Then the city grew,” explains Thomas. “Around the 12th and 13th century, there was a big demand for stone, because there was a spike in the population of Paris and of religiosity.”
The Notre Dame cathedral was built around this time, along with several other churches, all of them needing stone, which meant digging further underground. Initially, the quarries were far outside the city, beneath fields. But then the city expanded and those fields became city streets.
“Paris, as it grew, was built over the old quarries,” says Thomas. And over the years, people forgot about the quarries and continued to build on top of them - until they started collapsing.
That’s where Guillaumot comes in. An architect for King Louis XVI, he was appointed 334 years ago on 4 April 1777 as the city’s first Inspecteur des Carrières, Quarries Inspector.
He was given three tasks, explains Thomas, “to look for all the empty spaces under Paris; to make a map of them; and to reinforce anything under public streets and buildings belonging to the king.”
“Before the year 1777, the temples, palaces, houses and the public streets of several parts of Paris and its surrounding areas, were about to sink into giant pits,” Guillaumot wrote in a 1797 memoir.
He quickly realised that reinforcing the quarries was a long-term project, so he needed to put a system in place.
“Neither I nor my collaborators will see the end of it,” he wrote. “Others will have this opportunity, but I have reason to believe that we have paved the road for them, and they will not have any fundamental changes to make on the system that I implemented.”
The system involved building walls - underground – along the perimeters of buildings, which still exist today.
A limestone quarry under the Cochin hospital in the 14th arrondisement still exists today, maintained by an association that has an agreement with the city to renovate and maintain it.
Gilles Thomas works with the association, and insisted on giving a tour, saying that the only way to truly appreciate the history of the quarries is to see it for yourself.
The Cochin quarry is not far from the official catacombs, which are open to the public, but it is certainly not as easy to find.
Navigating through the hospital’s emergency room entrance, winding through the hospital grounds, Thomas heads into an underground parking area where there is a non-descript door.
Behind the door is a room with old photos and maps of what’s underneath the streets: blue for the empty spaces, brown for the masses left to hold up the quarry ceilings, all laid out in a rough grid.
Another door leads to a long concrete stairway that was built in the 1930s when the city turned underground spaces under administrative buildings into bunkers.
And about 20 metres down is the entrance to the quarry.
Unlike the public catacombs, which are mainly hallways packed with human bones, this quarry has open spaces with columns. The walls are limestone, the ground is packed dust. Street signs are engraved on columns and walls.
“When you are above ground, you can ask people for directions,” Thomas points out but in the 18th century Guillaumot and his workers had to wander in the dark, holding candles to light their way.
Traces of the first quarry inspector are everywhere, as each reinforcement wall and pillar has a code engraved on it, like 1G1786, which indicates the first column built by Guillaumot in 1786.
Every engraving had a date, but Thomas says you will be hard-pressed to find 1789, the year of the French revolution.
“You’ll see 1777, and years during the revolution, but there are very few from 1789, because it was year when there were other things to think about,” he says.
Guillaumot was imprisoned during the revolution, and removed from his position because he had been appointed by the king.
Later, in 1795, he was given his job back. He reappears on inscriptions with dates referencing the republican calendar, which was introduced between 1792 and 1806. The inscription 22.G.12R indicates the 22nd column built by Guillaumot during the 12th year of the French republic.
Thomas says the work of the Quarries Inspector continued through all of the upheavals of French history.
“Whatever the troubled history in Paris and in France, there was always being work done the quarries - during the revolution, during the terreur,” he says.
And traces of this remain: street signs with scratched-out fleur de lys, the royal symbol, because in 1793, anything having to do with royalty was systematically destroyed.
Or not quite everything. Ten signs with fleur de lys remain underground.
“There are so few, that there is an explanation for each one,” he says. The one above the number 270, for example, survived because it was in a pool of water. Another one was on the back of a sign that had been recarved.
In 1794, all references to religion were destroyed. Signs for streets named after saints, like Rue Saint Jacques or Rue Saint Paul were changed, above and below ground.
“The plaques made during the revolution just say Rue Jacques,” says Thomas. “And during the restoration, as there is no room between Rue and Jacques, some just carved a little “St” over it.”
Vestiges of this still exist above ground. Look closely at the stone carved street signs on the corner of Rue du Faubourg Saint Jacques and Rue Fossés Saint Jacques, you can see that the Saint was scratched out and put back. The same exists on Rue Saint Paul in the Marais.
Nearing the end of the tour, we come across members of the association setting up an underground lunch, taking a break from their renovation work.
And then it was time to walk back through the ages: through the 19th-century tunnels, up the 20th-century stairwell and into the air of the 21st century.
Visit underground Paris:
The Catacombs run by the City of Paris were built at the end of the 18th century, house bones excavated from cemeteries cleared out to build the city. Address: 1, avenue of Colonel Henri Rol-Tanguy, 75014
Occasional group visits of the Cochin quarry are organised by the Seadacc organisation. See its website (in French) for contact information.