Biggest ‘dig of the century’ beneath Notre-Dame: Roman coins, pottery and 1,700 years of hidden Paris history uncovered

An important dig below Notre-Dame is speculated to be the "dig of the century" for it uncovered around 1,700 years of Paris history in the cathedral's forecourt. Archaeologists hit Roman layers and found lots of stuff, such as a fourth-century coin, odd-marked medieval pottery, and old house remains. These finds show how the Île de la Cité became a Roman area, then a medieval spot, finally ending up as Notre-Dame’s location. This project gives researchers and visitors key original clues that change local history. There are also cool chances for dating, keeping things safe, and showing it off to the public. Beyond revealing nearly 1,700 years of continuous occupation, the excavation is helping archaeologists reconstruct how generations of Parisians lived, traded, built, and adapted to the city’s changing landscape, making it one of the most significant urban archaeology projects undertaken in modern Europe.

What archaeologists found beneath the cathedral: Coins, pottery and Roman layers

According to a press release by République Française, this excavation matters because it reveals a continuous record of human activity right in the heart of Paris. The Roman layers show that Lutetia spread farther than we thought, while Merovingian and Carolingian remains reveal the area was key for religious and residential purposes long before the cathedral came along.

The oldest levels date back to the beginning of Antiquity. Our teams uncovered the floor of a residence dating from the very beginning of the 1st century at a depth of 3.50 m in the Soufflot crypt at the heart of the cathedral. From the time of the Late Roman Empire, housing and craft artefacts (burnt soil and wood) have been discovered under the square.

With intact tombs, household trash, and construction waste, researchers get a firsthand look at everyday life, trading, and building methods through the centuries.

According to the Ministry of Culture and Institut National de Recherches Archéologiques Préventives (INRAP), “Stratigraphic layers reveal streets, houses and religious structures that predate the cathedral’s construction,” as well as “A fourth‑century coin and undeciphered pottery markings offer direct evidence of how Lutetia transitioned into medieval Paris”

Among the unearthed burials, a fully preserved anthropomorphic lead sarcophagus was discovered. Initial analysis of the grave goods found in the overlying fill layer suggests that this burial dates back to at least the 14th century. Given the characteristics and location of the sarcophagus, the hypothesis that it was the burial of a high-ranking official seems likely. Such a consistent timeline is super rare in a big European city, making it a fantastic benchmark for dating other sites in Paris.

How experts dated the finds and what official reports say

Dating relied on a combination of numismatic analysis (the fourth‑century Constantine coin), ceramic typology (pottery shapes and manufacturing marks), and stratigraphic correlation with known Parisian building phases.

Primary reports from the excavation team note that the coin’s mint mark and wear pattern anchor the upper Roman layer to the early fourth century, while pottery from the same stratum matches known late‑Roman wares. For top-level accuracy, the team cross‑referenced soil samples with dendrochronology results from nearby medieval foundations. These methods together provide a robust chronology that can be used in future research and museum interpretation.

What this means for visitors and the cathedral’s reopening

These findings will affect how visitors will experience Notre-Dame when it reopens after restoration. Authorities plan to set up an on-site archaeological garden and interpretive centre by the Soufflot crypt. They'll showcase important items like the lead sarcophagus, a fourth-century coin, and some pottery pieces there.

This setup allows the public to view the Roman floor and medieval foundations where they originally were. Plus, information boards and digital reconstructions will help visitors picture the transformations the area went through. By linking these physical remains to the history of the cathedral, they become an integral part of the site’s ongoing story. This helps us get a grasp of why Notre-Dame was built in this particular location and gives insight into 1,700 years of Parisian life.

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