A medieval lover’s dream: a ducal castle discovered in Brittany has captured the imagination of archaeologists

Details of the life and traditions of the Kingdom of France have become known

In an exciting discovery for archaeologists, the long-lost Château de l’Hermine in Vannes has been discovered, providing insight into the grandeur of France’s medieval region of Brittany.

A team of Inrap archaeologists commissioned by the French city of Vannes has just excavated the remains of the castle of l’Hermine, built by Duke of Brittany Jean IV in the 1380s. The excavations revealed a façade, various rooms, and several staircases, including a remarkably preserved ceremonial staircase consisting of a decorated core and three steps, as well as an upholstered window. All this allows archaeologists to draw the first plan of this building.

The archaeological work was carried out by order of public services in anticipation of the construction of the future Museum of Fine Arts of the city of Vannes.

The first phase took place between February and April 2023 in the cellars and current courtyard of the Lagorce Hotel, built at the end of the 18th century on the ruins of a medieval castle. The second phase of excavations, carried out in the fall of 2023, allowed the expansion of the excavation area and the completion of observations in the courtyard of the current building.

An archaeological survey carried out by Inrap in 2021 revealed that the stonework of the medieval building remained beneath the mansion. Under a thick mound of 2.5 to 4 meters, archaeologists unexpectedly discovered the first floor of the building. The entire building has a “veranda-house” plan, similar to the plan of the Castle of Susinio, the residence of the Dukes of Brittany in the second half of the 14th century. The living space is partially located above the passage in the towers, the architecture of which combines residential functions (chimneys and latrines) and defensive functions.

Excavations gradually revealed the ground floor plan of the ducal residence, 42 meters long and 17 meters wide, with exceptionally thick walls reaching 5.60 meters. It is immediately bordered by a moat and flanked on the east by what is described as a “square tower”.

In the thick masonry at each end of the house, archaeologists also discovered many latrines and drainage pipes belonging to the upper levels. Therefore, the castle must have had three or even four floors. The pipes lead to a pit that rises above the inner moat.

The excavations also revealed the presence of a mill, integrated – in a very original way – into the living space, in the “square tower” room that continues the eastern gable of the house. Elements of the mill have disappeared, but the location where the wheel was set into the masonry may have been revealed.

The uniformity of materials used to build the castle and the standardization testify to the mastery of the management of the site throughout the entire production chain – from quarrying the stone to its sale.

About a hundred worker marks were found on the stones to organize the construction: they reflect this consistent and controlled architectural program. The facade of the house has a stripe around the entire perimeter, which emphasizes the opulence of the building, as do the decorative details found on the jambs of the openings and even on the stairs.

The construction of the building took place in one stage, which demonstrates the importance of the financial and human resources used. The excavations indicate that Duke Jean IV knew how to surround himself with the best engineers and craftsmen of the time.

In 1365, Duke John IV signed the Treaty of Guerande, ending more than 20 years of conflict between the Penthièvre family and de Montfort’s supporters, and inherited the Duchy of Brittany. In 1381, he undertook the construction of fortresses throughout the duchy to assert his power.

In Vannes, the construction of the castle of l’Hermine, which became one of the strongholds of the duchy, was part of the expansion of the fortifications of power to the south.

Known as one of the favorite residences of Duke Jean IV, the castle of l’Hermine was intensively used for barely a hundred years and was abandoned afterwards. Almost absent from the archives, the building appears in ruins only on 17th-century plans.