Archaeologists Uncover Medieval Castle Hidden Beneath a French Hotel

Excavations revealed a moat, pipes, jewelry, coins and other artifacts amidst the structure’s ruins

The castle's mill was integrated into the residential space and powered by a canal that flowed beneath the building. Emmanuelle Collado / INRAP

Researchers have excavated the ruins of a medieval castle buried beneath a French hotel. Alongside the structure’s foundations, they found jewelry, staircases and even a moat, all offering new insights into the lives of the aristocrats who once lived at Brittany’s Château de l’Hermine.

Located in Vannes, a village in western France, the castle was built in 1381 at the request of John IV, the Duke of Brittany. At this time, Brittany was “essentially a tiny country” ruled by a series of dukes, as Live Science’s Kristina Killgrove writes.

Excavations Wide
Excavations were ordered ahead of the construction of a new art museum on the site. Emmanuelle Collado / INRAP

The Château de l’Hermine was one of John IV’s favorite residences, according to a translated statement from France’s National Institute of Preventive Archaeological Research (INRAP), which facilitated the recent excavation. Despite his fondness for the fortress, his grandson, Duke Francis II, abandoned it when he moved his residence to Nantes in the 1470s.

In the centuries that followed, new construction buried the structure. The recent excavations took place in the courtyard and cellars of the Lagorce Hotel, a mansion built in the late 18th century above the castle’s remains.

Researchers found several staircases, including this one leading into the mill room. Rozenn Battais / INRAP

Archaeologists were surprised by how well the medieval ruins had weathered the centuries. As CBS News’ Emily Mae Czachor writes, the castle’s “advanced architecture, structural complexities and sheer size” suggest that John IV “took construction on this dwelling space quite seriously.”

The castle was 138 feet (42 meters) long and 56 feet (17 meters) wide, and some of its walls were as thick as 18 feet (5.6 meters), per the statement. Excavations revealed several flights of stairs, including a “remarkably preserved” ceremonial staircase with space for a window seat. The team also found toilets and drainage pipes, and the placement of the pipes suggests the original structure had up to four floors.

Excavators combed the moat, which was lined with secure stone walls. Emmanuelle Collado / INRAP

The Château de l’Hermine was “a castle surrounded by water,” according to INRAP. A canal once flowed beneath the building, carrying water from the Marle River; its current powered a residential mill, a wheel that harnessed the energy of the flowing water to power a process like flour grinding. The mill’s wooden wheel did not survive, but researchers found the place where it once spun.

They also uncovered the mill room’s grated exit, where water would have flowed out to an exterior moat that bordered the fortress.

The moat revealed a trove of artifacts, including pins, clothing, shoe buckles, metal dishes, keys and padlocks. Per the statement, researchers also found the remains of an “essential” wooden bridge that enabled passage over the moat.

Le château de l'Hermine refait surface à Vannes (Morbihan)

The excavations began in 2021 ahead of plans to transform the historic Lagorce Hotel into a new branch of the Museum of Fine Arts, reports Live Science. Since then, archaeologists have been working to uncover the unexpectedly well-preserved remains.

“The homogeneity of the materials used for the construction of the castle and the standardization of the modules show a mastery of site management throughout the operational chain, from the extraction of the stone to its implementation,” writes INRAP. “The remains indicate that John IV knew how to surround himself with the best engineers and craftsmen of the time.”

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