 Around the trapezoidal inner courtyard, to the right is a corps de logis of more recent vintage, undoubtedly 18th-century; and on the left stand the domestic buildings, protected by a watchtower on the exterior facade, and a small 15th-century seigneurial chapel.The origin of Trécesson castle is lost in the mists of time.It was mentioned as the seat of the lords of Ploërmel and Campénéac from the 8th century.