Château de Poligny, Medieval fortress ruins in Poligny, France

Château de Poligny is a castle ruin in the French town of Poligny and contains sections of original walls, several defensive towers, and portions of medieval fortifications spread across the site. The layout reveals the original division into distinct functional areas that served different defensive purposes.

Girart de Roussillon had the fortress built in the 9th century on Mount Grimont, on the site of a Gallo-Roman temple to Apollo Gryneus. It was dismantled in 1643 under Louis XIII and Louis XIV, leaving only ruins.

The castle stands on Mont Grimont, whose Latin name Gryneus mons recalls a Celtic religious site and later a Gallo-Roman temple to Apollo Gryneus. In the Middle Ages the fortified border between the Kingdom of France and the Holy Roman Empire ran along this line of castles, from Château-Chalon to Arlay and Nozeroy.

The site lies on the Grimont hill above Poligny, at the entrance to the reculée and the Geneva road, so the approach is uphill on foot. The remains are scattered ruins rather than laid-out paths, and the ground on the slope is uneven. Sturdy shoes help; the walk up also gives the clearest view of the surviving wall and towers.

The castle was built on the site of a Celtic religious site that later became a Gallo-Roman temple to Apollo, called Gryneus, which gave the hill its Latin name Grynei mons. The perimeter formed a stronghold of about 3 hectares, enclosed by an 800 m wall and seven towers.