A team of restoration workers in Dijon, France, pulled up a section of stone flooring inside the Church of Saint Philibert and found a staircase that wasn’t on any of the plans. It was just one of the many surprises the church had to offer.

What started as routine repairs soon turned into a full archaeological excavation, revealing a 400-year-old burial vault — and then tombs, churches, and sarcophagi spanning more than a thousand years of history. The findings stunned researchers, linking modern day to the Middle Ages and even the Roman Empire.

Heat, Salt, and a Church

The excavation began not because anyone wanted to find ancient relics, but because of salt — specifically, salt that had been quietly destroying the church from below.

In the 1970s, someone made a rather unfortunate decision to install a heated concrete slab. The problem was that the slab trapped a bunch of salt under it, as the 800-year-old church was used for salt storage in the 18th and 19th centuries. The heating and cooling of the salt started to cause cracks and damage to the church. Eventually, it was decided that repairs were necessary.

The repairs required digging into the church’s foundations. But, the more restorationists dug into different places, the more they came across different, unexpected things. That’s when archaeologists started looking more closely.

First, they found coffins and burial sites. In the nave, several such coffins were found, dating from the 14th to the 18th centuries, all aligned in an east-west direction. There were almost no grave goods along with them. Then, in the transept, they found a vaulted burial site from the 15th to 16th centuries. These contain remains that had been moved, likely to make room for new burials. But this was still only the beginning.

Underneath, they found additional graves dating back to the 11th century, before the church was even built. And below those, six ancient sarcophagi emerged — some from the Merovingian era (6th–8th centuries), others possibly even older. All this, in a church built in the 12th century.

Layers of History

At first glance, this seems hard to explain. However, beyond the tombs, the team uncovered architectural traces that predate the current Romanesque building. The oldest is believed to be from the 10th century, based on walls constructed in opus spicatum, or herringbone masonry — a style typical of the Early Middle Ages.

Even before that, archaeologists say, the place would have been a site of worship.

The 12th-century Church of Saint Philibert was not built in isolation. It was layered atop earlier sacred spaces, each one erected, used, and then buried by the next. Over time, these structures became entombed in the very ground they once stood on.

In many Christian sites in Europe, it’s quite common for churches to be built on top of older religious structures. As communities evolved, new churches were often constructed over earlier ones to reuse sacred ground. New churches were built to reflect changing architectural styles, to accommodate growing populations, or simply because the old ones were unusable.

This practice goes all the way to the origins of Christianity. In many cases, Christian churches were even built atop earlier Roman temples or pagan sanctuaries, symbolically asserting the dominance of the new faith. The layers uncovered at Saint-Philibert are a striking example of this historical pattern.

Reconstructing a Forgotten Churchscape

While archaeological digs are common across Europe, few offer the kind of time-spanning vertical record seen at Saint-Philibert. From late antiquity to the modern era, the church’s foundation has preserved an evolving story for the region. The findings are valuable, and researchers are now considering how to best reconstruct and preserve the findings. There’s also a bit to research more closely.

In particular, a few sarcophagi that seem to be around 1,500 years old. Based on current research, these sarcophagi appear to have been placed inside one or more buildings that were in use between Late Antiquity and the Early Middle Ages. This transitional period from the Roman Empire to the Early Middle Ages isn’t fully understood. Meanwhile, the presence of Merovingian-era sarcophagi within a Romanesque church reveals how early Christian customs were woven into later medieval institutions.

Ultimately, Saint-Philibert’s history is still being written. The church has undergone multiple renovations over the centuries, and apparently even some reconstructions. Yet the most transformative chapter may be the one being uncovered right now. The church is set to become more than a place of worship: it’s becoming a time capsule of how the region in France changed.

For the archaeologists involved, this isn’t just a dig. It’s a rare chance to follow time itself down a stairwell few knew existed.