“When we arrived, there were still the basketball hoops. Supporting photos, Thomas Arnoux shows what the excavation site looked like before the Inrap teams invaded it at the beginning of January. The regional delegate of the National Institute for Preventive Archaeological Research shows images of an old schoolyard covered in bitumen which served as a game board, but also as a parking lot. It is here, at the foot of the former Adoration College, in Rennes (Ille-et-Vilaine), that archaeologists made an astonishing discovery. While digging with a mechanical shovel to examine the bowels of the Breton capital, the scientists came across the remains of an old shale quarry. A rare element in a city yet accustomed to sensational archaeological discoveries.
The proliferation of construction sites has recently enabled Inrap to unearth hundreds of tombs, including the remarkable one of Louise de Quengo. But this is the first time that his teams have encountered such a monument. Just imagine: the stones that were extracted here were used to build the first streets of what was then called Condate. Dating: between 50 and 150 AD. 2,000-year-old remains hidden there, under our feet, and which will soon be overlooked by a senior residence. “Shale stones are very draining materials. They were used to shape the foundations of streets and buildings because they easily evacuate water”, explains Nicolas Menez, the site manager.
Mysterious holes in the stones
His teams even discovered a multitude of holes in the stone. These would be crowbar impacts that the Romans used to extract rock. The technique still exists in modern quarries, but it is done explosively. Green in color, the shale discovered here is very friable. It is a cousin of the purple shale that was used to build so many houses in Rennes from medieval times and can still be seen today.
Discovered close to the city center of Rennes, these remains remind us of how narrow Condate was at the time. Imagine that this quarry was not even in the Gallo-Roman city. “We put the craft activities outside the city because they were considered noisy, fragrant and they risked causing a fire”, explains the archaeologist of Inrap.
A dump and treasures
Two thousand years later, the old quarry is submerged in the middle of residential buildings and covered by three meters of earth, and a few centimeters of bitumen. Probably closed in the 3rd century, the quarry then became a kind of dump where the inhabitants came to throw away their broken or damaged trinkets. While digging, the archaeologists were able to cross the path of various objects: a sestertius stamped with the profile of the Roman emperor Trajan, who died in 117 AD. Or a statuette of Venus in terracotta, probably shaped in Bourgogne.
Opened at the end of January, the Inrap excavation site will close at the end of April and will give way to the property developer for the construction of a senior residence. A new life for this space which has long housed a convent. The story does not end there.