Château de Clermont, Medieval castle ruins in Chirens, France

Château de Clermont is a ruined castle on a hilltop near Chirens with the remains of a stone keep and triple defensive walls in an irregular pentagonal shape. The structure reveals different building phases and medieval fortification systems.

The castle was founded in the 11th century by the Clermont-Tonnerre family and shaped the region for centuries. It was destroyed in 1626 on Cardinal Richelieu's orders and never rebuilt afterward.

The castle gave its name to the Clermont family, later Clermont-Tonnerre, which still owns the keep. In 1203 Guillaume de Clermont sold the castles of Clermont and Saint-Geoirs to the Archbishop of Vienne and received them back as a fief. A local legend claims a tunnel links the ruins to the Château de Montclair opposite, with hidden treasures beneath the rubble.

The ruins stand at 637 m on the Clermont hill, 1.5 km west of the village of Chirens; the site is reached on foot and the ground around the keep is uneven. From the hilltop the valleys of the Ainan to the east, the Fure to the west and the Voiron and Isère valley to the south are visible, but the Lac de Paladru is not.

The keep is irregularly pentagonal, an uncommon shape for a medieval tower, and still belongs to the Clermont-Tonnerre family. A local legend claims a tunnel links it to the nearby Château de Montclair, with exits in certain houses and treasures buried under the rubble.