Archaeologists excavating a 750-square-metre plot on Montbellant hill in Tonnerre, in France’s Yonne department, have uncovered successive remains spanning more than 1,500 years. The work, conducted by France’s National Institute for Preventive Archaeological Research (Inrap), is taking place before construction of a detached house.
In some areas, archaeological deposits extend more than two metres below the surface. Researchers are excavating the layers sequentially, moving through medieval, Roman and Iron Age occupation before reaching the underlying limestone. The site is less than 50 metres from an Inrap excavation carried out in 2024, which also produced evidence for the development of early Tonnerre.
The uppermost remains include a large medieval building, probably dating to the middle medieval period. It contained several rooms and had been altered repeatedly. One room included a cellar cut partly into the limestone, with access provided by a stone staircase. The cellar was later filled, while a second, older subterranean structure dating to the Roman period survived nearby.
Another room contained a partly excavated vaulted entrance facing toward the valley. The entrance appears to have collapsed into an earlier pit beneath it, pulling sections of the wall and vault into the cavity. Excavators recovered wedge-shaped stones from the arch and an iron fitting between two facing stones, evidence that the entrance had once held a wooden door.
Below the medieval structures, archaeologists have identified several ancient buildings. Some walls remain standing above their original floor levels, and one structure appears to have been associated with a courtyard surface. Fragments of metallurgical slag are widespread across the excavation, suggesting that a metalworking workshop may have operated nearby, although the functions and full plans of many buildings remain uncertain.
The deepest occupation identified so far dates to the first century BC, when Montbellant hill formed part of a Gallic oppidum. Pits and other features have survived despite later construction, and pottery and coins from them indicate that an organised community occupied the summit before the Roman period.
The evidence suggests repeated redevelopment rather than a series of entirely separate settlements: Roman structures altered or replaced earlier remains, while medieval construction cut through both ancient and Iron Age deposits. Archaeologists expect further excavation to clarify changes in buildings, streets, industrial activity and domestic spaces. The site is scheduled to open to the public on September 3, 2026, while excavation is still under way.
