Archaeological teams working beneath Notre Dame cathedral in Paris have uncovered artifacts spanning nearly 2,000 years of history, as part of excavations required before the installation of new landscaping in the cathedral's forecourt.

The dig, which extends 4 meters (13 feet) underground, has revealed layers of Parisian history from Roman times through the medieval period. Among the most significant discoveries is a fourth-century coin bearing the image of Roman Emperor Constantine, along with medieval pottery fragments containing mysterious reddish markings that experts have yet to decipher.

The excavation became necessary as Paris plans to redesign the square in front of Notre Dame, adding trees and cooling features as part of climate adaptation efforts. The new landscaping, expected to be completed by 2028, will include 160 trees and water features to provide relief from increasingly hot summers. However, city regulations require archaeological investigation before any construction work can begin in areas with potential historical significance.

Archaeologists have identified distinct historical layers in the soil, including medieval cellars from houses that once crowded the square, Merovingian and Carolingian grain storage pits from the sixth to tenth centuries, and Roman-era remains from the fourth and fifth centuries. The site represents the ancient center of Paris on the Île de la Cité, where the city first developed around 2,000 years ago.

Many of the best-preserved artifacts have come from medieval waste pits that served as both latrines and garbage dumps. The soft organic material in these pits helped preserve complete pottery vessels, jugs, and cups that would normally have been broken over the centuries. The mysterious markings found on pottery shards have particularly intrigued researchers, as they appear repeatedly but remain undeciphered.

The Roman-era findings are considered especially valuable by the research team, as they provide insight into Lutetia, the Roman settlement that preceded modern Paris. Evidence suggests that as the Roman Empire declined, residents consolidated on the fortified island where Notre Dame now stands, often repurposing stone from earlier buildings for new construction.