Workers repairing a damaged floor inside the Church of Saint-Philibert in Dijon, France, lifted a stone slab and found a staircase that appeared on none of the building’s plans. The staircase led to a sealed burial vault that had sat undisturbed for at least 400 years, and below it, layer after layer of tombs, sarcophagi, and buried architecture stretching back more than a millennium.
The church dates to the second half of the 12th century and is the only surviving Romanesque structure of its kind in Dijon. The repairs were not driven by archaeology but by structural damage traced to a poorly planned 1974 renovation, which had installed a heated concrete slab over floors saturated with centuries of salt. When workers pulled up that slab to assess the damage, the staircase emerged beneath it.
Researchers from the French National Institute for Preventive Archaeological Research (INRAP) were brought in to investigate. What began as a structural assessment became a full excavation, planned to reach a depth of three meters.
A Bad Renovation and Centuries of Hidden Salt Damage
Saint-Philibert was deconsecrated after the French Revolution and repurposed as a salt warehouse during the 18th and 19th centuries. That use left heavy salt deposits embedded in the stonework throughout the building. The salt itself was not immediately destructive, but the 1974 renovation changed that.
When a heated concrete slab was installed that year, the cycling heat caused the trapped salt to expand and contract repeatedly, cracking the church’s foundations from below. The damage accumulated over decades and eventually required intervention. Removing the slab to assess the extent of that damage was what exposed the hidden staircase and set the excavation in motion.
The decision to bring in INRAP archaeologists proved consequential. The more workers dug into different areas of the church, the more unexpected material surfaced. A routine structural repair had opened access to more than a millennium of history layered beneath a single building.
Bones Pushed Aside to Make Room for the Dead
The staircase led to a sealed burial vault in the church’s transept, which INRAP dated to the 15th or 16th century. According to the agency’s press release, the vault held the remains of both children and adults, interred in wooden coffins. Over time, bones had been pushed to the sides of each coffin to make room for newer burials, a practice consistent with communal vaults of that period.
Most of the deceased were adults dressed in shrouds. “Very few objects were found in the tombs apart from rare coins and two rosaries,” INRAP stated. The vault’s foundation measured roughly nine feet in depth, and six sarcophagi were also recovered from the site.
The density and arrangement of the burials led some researchers to raise the possibility that those interred may have died during a significant event such as a pandemic or famine. INRAP did not confirm that interpretation and presented it as one possibility rather than a conclusion. Further analysis of the remains would be needed to say more.
The nave of the church produced additional coffins dating from the 14th to the 18th centuries, all oriented east to west and containing almost no grave goods. Together with the transept vault, the nave burials established that Saint-Philibert had served as an active burial site across several centuries before its deconsecration.
Six Sarcophagi and a City Built Over Its Own Past
The vault was not the oldest thing the excavation uncovered. Beneath the 15th-16th century burials, archaeologists foundslab tombs dating from the 11th through 13th centuries, predating the current Romanesque building. Below those were six sarcophagi attributed to the Merovingian era, roughly the 6th through 8th centuries, with some possibly older still.
Architectural analysis of the site revealed walls built in opus spicatum, a herringbone masonry style associated with the Early Middle Ages, suggesting a 10th-century building had stood on the same ground before the current church was constructed. INRAP said the site may have functioned as a place of worship even earlier, continuing a pattern common to Christian sites across Europe where successive sacred structures were built directly over their predecessors.
A group of ancient sarcophagi tentatively dated to around 1,500 years old appears to have been placed inside one or more buildings active between Late Antiquity and the Early Middle Ages, according to INRAP. Researchers said this transitional period from the Roman era to the Early Middle Ages is not fully understood, and the site’s vertical record spans from the 6th century to the modern era.
The excavation’s three-meter planned depth captured remains from multiple distinct historical periods stacked directly on top of one another. Each layer reflected a different community, a different era of construction, and a different relationship to the same patch of ground in what is now central Dijon.
A 1,500-Year Record Confirmed Beneath a Single Church Floor
The excavation remained ongoing as of INRAP’s published reporting. Researchers said they are examining how best to document, reconstruct, and preserve what was found across the vertical sequence of the site. The church, damaged and repurposed over centuries, is now being treated as a continuous archaeological record stretching from the present day back to at least the 6th century, and possibly to the Roman period.
The sarcophagi attributed to the Merovingian period and the architectural traces of earlier buildings add historical depth that was entirely unknown before the slab was removed. Few excavations in Europe, INRAP indicated, offer this kind of unbroken vertical record from Late Antiquity through the modern era within such a compact footprint.
INRAP confirmed the excavation revealed remains dating from Late Antiquity to the modern era within the planned three-meter excavation depth at Saint-Philibert, with work at the site continuing.