In a bustling city like Paris, history lies beneath the surface, hidden in its ancient grounds. Visitors to the Notre Dame Cathedral wait under the summer sun, ready to witness its iconic gargoyles. But beneath them, archaeologists are digging down, uncovering the remnants of Roman Paris from 2,000 years ago.

In 2019, flames took Notre Dame’s spire down, but the cathedral has been reconstructed, reopening to the public by the end of 2024. Paris aims to transform the current barren square in front of the cathedral into a cooler, shaded area, complete with trees. To preserve the historical grounds, extensive excavation is needed before construction begins.

A rare chance to impact the history of Paris.

Part of the Notre Dame square has become a bustling excavation site, surrounded by barriers with a wooden walkway bridging the gap to the waiting crowds. Some have dubbed it the “excavation of the century.” Lucie Altenburg, the conservator of Paris’s archaeology unit, emphasized the significance of these discoveries to the Associated Press.

The finds include hundreds of artifacts such as a fourth-century coin with Emperor Constantine’s visage and medieval ceramic fragments painted inside, yet to be deciphered, reminiscent of a modern ‘Code Da Vinci.’

Emily Carter, a 34-year-old tourist from Manchester, standing in line with her children, expressed how the findings add life to Notre Dame. Discovering another city beneath the feet evokes a profound sense of awe.

Initial traces appear a mere 50 centimeters (20 inches) deep. At four meters (13 feet) below, the team steadily uncovers the past, sometimes filling up to 15 boxes with earth untouched for decades.

In ancient cities, history resides beneath street level, built upon the debris of previous eras, causing the ground to rise over time. For instance, Rome has risen approximately nine meters (30 feet) since the fifth-century fall of the empire.

When Athens constructed its metro for the 2004 Olympics, it led to the largest archaeological excavation in Greek history, revealing tens of thousands of items showcased at metro stations. Paris, similarly, traces its origins back to Île de la Cité in the River Seine, where centuries later, Notre Dame emerged in 1163 amidst crowded medieval houses.

The excavation has reached these historic cellars, unearthing grain silos from the Merovingian and Carolingian periods, dating between the 6th and 10th centuries. In darker depths lie a dense Roman quarter from the 4th and 5th centuries—twenty centuries of history stacked in four meters of earth, or akin to one and a half Napoleons Bonaparte tall.

Yasmine Benali, a 22-year-old archaeology student, observes the relics from behind barriers, noting how the city feels less like a postcard and more as an ongoing discovery.

Archaeologists have found invaluable items within ancient latrines under medieval houses—jugs and cups tossed centuries ago yet preserved among broken plates and animal bones. Valentine Breloux, an archaeologist, remarked on the rarity of intact ceramics cushioned by soft waste, emerging whole after centuries.

Other mysteries intrigue the experts. Some medieval ceramics carry faint red writing inside, their meaning still unknown but promising new insights.

Coins surface encrusted with rust, but X-rays reveal them as Roman coins from Constantine’s reign in the early 4th century. Such artifacts help date the layers beneath the surface.

The Roman artifacts, deeply buried and oldest, are least understood. Back when the Roman empire flourished, Paris, known as Lutetia, centered on the Seine’s left bank. As the empire crumbled, the population drifted to Île de la Cité, later to be fortified by Notre Dame, using stones from earlier structures.

Colonna’s team discovered evidence—a Roman threshold recycled from a larger building, flipped and repurposed as pavement.

Each find journeys to Paris’s archaeology center, which Colonna portrays as a vast archaeological repository, a treasure trove of the city. For archaeologists, excavating the cathedral is a unique privilege. In France, similar to other locations, they only dig preemptively where construction is planned, akin to how quarry workers have unearthed dinosaur fossils.

The excavation happened because Paris decided to beautify the area, Altenburg explained.

By 2028, the newly planned plaza will be mostly ready. It will feature 160 new trees and water surging over stones to cool them in the summer, aligning Paris’s preparations for intensifying heat from climate change. Summers from now, tourists will queue in comforting shade under Notre Dame’s gargoyles.

The underground space will reopen as a visitors center with views of the Seine.

Until then, Notre Dame’s team aims to delve deeper, past Roman eras, toward the city’s original inhabitants—the Gauls who bestowed Paris its first name. Altenburg hopes to reach further back in time than ever before.

Note: Research for this article was contributed by Nicolas Garriga in Paris. This story was translated from English by an AP editor using generative AI tools.