Castle of La Roche-Guyon, Medieval fortress in La Roche-Guyon, France.

The Castle of La Roche-Guyon stands on a chalk cliff above the Seine, with a circular keep 35 metres high and 12 metres in diameter, its walls 3 metres thick, built between 1180 and 1200. A staircase of about a hundred steps cut into the cliff links it to the troglodyte castle. At the foot of the hill, the lower château has a regular facade of light grey stone, a steep dark grey roof with dormer windows and two brick chimneys, and a small projecting turret at the left corner.

A troglodyte castle was dug into the cliff at the end of the 11th century; Guy de La Roche added the circular keep (1180–1200), 35 m high with 3 m thick walls, and a lower manor followed in the 12th century. In 1419 Perrette de La Rivière surrendered to Henry V after a six-month siege. In 1944 Army Group B under Rommel and then von Kluge had its headquarters here until liberation on 25 August.

The name comes from the lords of La Roche, whose eldest sons were traditionally called Guy; roche means rock. The family held the castle until the end of the 15th century, when it passed by marriage to the Sillys, then to the La Rochefoucauld, raised to a duchy in 1622. Since 2010 contemporary works, such as columns by Daniel Buren, have been installed along the galleries and ramparts.

The site has two parts: the ruined keep on the chalk plateau, reached on foot, and the lower château with its terraces and kitchen garden beside the Seine. The upper keep and the staircase of about a hundred steps cut into the cliff involve steep, uneven ground, so allow time for the climb. The lower rooms, including the 18th-century salon, library and small theatre, are the accessible part of the visit.

The chapel's west nave is said to follow a sanctuary that Pience, widow of the domain's owner, had dug into the cliff after meeting Saint Nicaise in the 3rd century. A Merovingian necropolis found on the site shows a small community lived here in the early Middle Ages.