Built on a Gallo-Roman tumulus in the late 13C, it housed Marguerite de Valois, alias Queen Margot, and her lover in 1595, while they were wanted by the armies of Henri IV. After their departure, the chamber was walled up and only discovered by chance in 1990. In 1622, Louis XIII is known to have stayed here. The tour shows you 15 furnished rooms, including the queen's apartments.