This formidable fortress is protected by deep, wide moats and defended by towers with characteristic Breton pyramid-shaped firing slits. The graceful Tour de la Couronne d'or and the well, whose wrought iron decoration depicts the ducal crown, are particularly interesting. The Grand Logis features Gothic skylights and was built by François II to house the dukes of Brittany. The château is now home to the fascinating History Museum of Nantes.