Château de la Roche Jagu stands on a rocky promontory above the River Trieux about 9 km downstream from Pontrieux, commanding views down the wooded valley towards the sea. The castle dates from the early 15th century and is one of the best-preserved medieval buildings in the Côtes-d'Armor — its silhouette of towers and machicoulis is unmistakably military despite the elegant stone finish.
The grounds include formal gardens laid out on the terraced slopes above the river, replanted in a style consistent with the period. The interior has been partially restored and is open for visits; the upper floors give good views across the Trieux valley. Guided tours are available in summer.
The château is managed by the Côtes-d'Armor departmental council and entry is reasonably priced. It is easily combined with the Trieux river cruise — the boat passes below the castle, allowing you to see its position from the water.