Under Notre Dame, a 'dig of the century' looks to unearth thousands of years of Parisian history

More than a year after France's famed Notre Dame reopened to the public, an archaeological exploration delving into thousands of years of the history of Paris and dubbed by some as the "dig of the century" has begun just metres below the cathedral's ground floor. 

As the world watched on in 2019, a fire on Paris's Île de la Cité brought the cathedral's spire crashing down and sparked the beginning of a major process to rebuild and restore the medieval site.

The doors were thrown open once again in December 2024 at a lavish ceremony attended by French President Emmanuel Macron and more than 2,500 guests, such as then-US president-elect Donald Trump and Prince William.

Now Paris is seeking to continue the area's reformation by softening the hot, bare square located in front of Notre Dame with the addition of trees and shaded areas.

But in a city more than 2,000 years old, the soil cannot be turned until what lies beneath it is excavated, in case it is damaged during works.

So, a slice of Notre Dame's forecourt has become an excavation site — an open pit ringed by barriers and crossed by a wooden walkway, a few steps from the line-up.

Here is what excavators and archaeologists are hoping to find.

A window into the Paris of past millennia

Lucie Altenburg, a conservator with the Paris archaeology unit, told the Associated Press that the excavation underneath Notre Dame could develop the world's understanding of the city's past.

"It's a rare opportunity for us to work on something that's tangibly going to make a difference to the history of Paris," she said.

Excavators have already uncovered hundreds of historical artefacts, including a 4th-Century coin stamped with the face of the Emperor Constantine and shards of medieval pottery painted on the inside with marks no expert has yet deciphered — like a modern Da Vinci Code.

"It makes Notre Dame feel alive again," Emily Carter, a 34-year-old tourist from Manchester, said.

The first traces of Parisian history appear 50 centimetres under the surface of Notre Dame. Four metres lower than that, the archaeological team is still pulling up the past.

Some days they fill 15 crates with artefacts from the ground that has lain untouched for decades.

At the cathedral's birth in 1163, the entire square located on an island in the middle of the River Seine was packed with medieval houses, split by a single street, according to Camille Colonna, the archaeologist leading the dig.

During the excavation, her team has reached the cellars of Paris's medieval residents — and therefore also the time in history they represent.

Below them lie Merovingian and Carolingian grain pits, from the 6th to the 10th centuries; below those, darker and deeper still, a dense Roman quarter from the 4th and 5th centuries.

Twenty centuries are stacked in four metres of earth — or about the height of two-and-a-half Napoleon Bonapartes standing on top of one another.

"Here you can see the layers — medieval Paris, Roman Paris, maybe even before that," Yasmine Benali, a 22-year-old archaeology student who watched the dig from behind barriers, said.

Mysterious discoveries buried deep in medieval waste

The richest finds appear to have come from the foulest places: the deep pits beneath the medieval houses, old latrines that doubled as rubbish dumps.

Out of them, excavators have lifted whole jugs and cups — thrown away centuries ago, yet still intact — among broken plates and animal bones.

It's "rare to find complete ceramics," Valentine Breloux, an archaeologist with the unit, said.

Soft waste in the soil cushioned them, and centuries later, they miraculously came up whole.

Then some other objects came that confounded experts.

As conservators cleaned what looked like ordinary medieval pottery, they found faint reddish writing painted on the inside — the same mysterious markings on shard after shard.

What they mean has yet to be deciphered.

Of everything she has cleaned from Notre Dame, Ms Breloux said these were the most "astonishing."

The coins came up as black discs, eaten by rust, but under an X-ray, a face returned: it was Constantine, the Roman emperor who ruled in the early 300s AD.

Such objects also "can be invaluable in giving us the date of the [underground] layer," Ms Altenburg said.

What did the Romans ever do for Paris?

The Roman finds are the ones the archaeologists value most — the deepest, oldest, and least understood.

In Roman times, the town was called Lutetia, and its centre lay across the river on the Left Bank.

As the Roman Empire collapsed, people pulled back to the Île de la Cité and fortified the island with walls of stone taken from earlier buildings.

Ms Colonna's team found proof, including a Roman doorstep found in the dig that appeared to have been taken from a much bigger building, carried over, turned upside down and laid in a road as paving.

Every find leaves the pit and travels north to the city's archaeology centre — what Ms Colonna called "a huge archaeological store" — a treasure house of Paris.

For archaeologists, the cathedral dig is a rare treat. In France, like elsewhere, they work only where building work is about to begin in a similar method to industrial quarry workers who unearth dinosaur remains.

"This only happens because the city of Paris decided it wanted to beautify the area," Ms Altenburg said.

The new square should be mostly finished by 2028 and include a woodland clearing with 160 new trees and a thin film of water sliding over the stone to cool it in summer.

The plan forms part of how Paris is bracing for ever hotter summers induced by global warming.

The tourists who wait in the sun beneath the gargoyles will, in a few summers, line up in the shade.

The old underground parking lot will reopen as a visitor centre looking onto the Seine.

Until then, the Notre Dame team wants to dig deeper — past the Romans, toward whoever came before them, the Gauls who gave the city its first name.

This is the bargain in every old city: the past is not in a museum down the street — it is under the street.

Cities rise, each age builds on the rubble of the last, and the ground climbs with it; in Rome, it has risen about 9 metres since the empire fell in the 5th Century AD.

When Athens built its metro for the 2004 Olympics, it set off the largest excavation in Greek history and turned up tens of thousands of objects, now shown in the stations themselves. 

Paris is no different.

AP