PARIS — Beneath the iconic Notre Dame Cathedral in Paris, archaeologists are uncovering layers of the city’s history dating back nearly 2,000 years. Since 2019, when a devastating fire destroyed the cathedral’s spire, the structure has undergone reconstruction and reopened in late 2024. Meanwhile, plans to transform the cathedral’s forecourt into a shaded green space have prompted a major excavation to safeguard the archaeological remains buried beneath the historic site.

Located on the Île de la Cité, the heart of ancient Paris, the excavation site is a fenced pit crossed by wooden walkways, situated just steps from the lines of tourists queuing to enter the cathedral. Archaeologists have described the project as a “dig of the century” due to the exceptional density and continuity of historic layers beneath the square.

Lucie Altenburg, a conservator with the Paris archaeology unit, said the excavation offers a unique opportunity to deepen understanding of Paris’ origins. “It’s a rare chance to work on something that is tangibly going to alter the history of Paris,” she said.

The dig has produced hundreds of artifacts spanning centuries. Finds include a fourth-century coin bearing the likeness of Emperor Constantine, medieval pottery shards painted with unexplained reddish markings, and remarkably well-preserved ceramics retrieved from deep latrines beneath medieval houses. These waste pits served as dumps but inadvertently cushioned fragile vessels, allowing them to survive intact through centuries.

The archaeological layers reveal a continuous timeline beneath just 13 feet of earth. Close to the surface are remnants of medieval Paris, including house cellars dating back to the 12th century when the cathedral was first built. Below them lie grain pits from the Merovingian and Carolingian eras, roughly spanning the 6th to 10th centuries. Deeper still is a dense Roman quarter from the 4th and 5th centuries, revealing aspects of Lutetia, the Roman city that occupied the area before Paris emerged.

Archaeologists have also uncovered evidence of Roman reuse of building materials, such as a repurposed doorstep inverted and embedded into an old road, indicating how inhabitants adapted structures during the empire’s decline and retreat to the island fortress.

Artifacts recovered during the excavation are transported to the Paris archaeology center, described by the lead archaeologist Camille Colonna as a vast repository and research facility. The work is unusual in France, where digs typically coincide with construction projects, making this proactive urban renewal project a rare chance for comprehensive study.

The forecourt’s redevelopment aims to address climate challenges with the planting of 160 new trees and the installation of a fine misting system to reduce summer heat. The space should be completed by 2028, offering visitors shaded areas near the cathedral, as well as a reopened underground parking area converted into a visitor center with views over the Seine.

While present efforts have reached the Roman layers, researchers hope to extend the excavation further to explore earlier settlements, possibly dating back to the Gauls, the original inhabitants who named the city. Altenburg expressed optimism about the future of the dig: “The hope is that we are able to go back in time even further than we’ve ever been before.”