The operation was carried out as part of preventive archaeology prior to the construction of the Museum of Fine Arts of the City of Vannes, and while the owners were aware of the medieval structure under the Hôtel Lagorce, the scope, and preservation of it were a surprise to everyone involved.

The first phase of the project took place between February and April 2023 in the cellars and courtyard of the hotel which was originally a private mansion built at the end of the eighteenth century.