Timeline

Heritage classified

Key figures

Origin and history

The citadel of Montreuil-sur-Mer found its origins at the end of the 12th century, when Philippe Auguste abandoned a castral motte to erect a polygonal Philippian castle with eight towers, without dungeon. This royal castle, from which remains the castle with two massive towers and elements of courtines, would have inspired the fortresses of Boulogne-sur-Mer and Hardelot, built by his bastard son Philippe Hurepel. At the beginning of the 14th century, the urban enclosure developed with works such as the Queen Berthe tower (15 m in diameter), equipped with a guard corps and a renovated room in the 16th-17th centuries. This tower, later integrated into the citadel, marked the southwest entrance of the fortified city, supplemented by three other towers (F, E, and Blanche) connected by courtesines.

The transformation into a bastioned citadel began after 1537, when François I modernized the defences of Montreuil, destroyed by Charles Quint. The Philippian castle was strengthened under Charles IX (1567), then reshaped into an irregular star with five bastions around 1600 by Jean Errard. In the 17th century, Vauban, although considering Montreuil as a third-place site, added an arsenal, half a moon on the city side, and reworked the ice. The citadel loses its strategic role after the displacement of the borders, but its round path (XVIth-17th centuries), juised over the Canche Valley, offers a view of the river, the lighthouse of the Touquet, and coastal towns.

In the 19th century, the citadel became the Coligny barracks, hosting a military preparatory school for troop children (1886–1914). During the First World War, it was home to the British Grand Headquarters in 1916, with its casemates serving as a transmission centre. After 1924, the site, decommissioned militarily, was opened to the public by the association Les Amis du Vieux Montreuil, which installed a museum and library. The German occupation (1939–1944) dispersed collections and degraded buildings, before the site became a youth hostel in 1946.

Ranked a historic monument in 1926 (for its enclosures and the Queen Berthe Tower) and in 1913 (for its ramparts), the citadel also includes a German underground complex of the Second World War, registered in 2012. Since 1926, it has been protected for its natural heritage, notably as a Natura 2000 site with a colony of Grand rhinolophe. Today, the tour mixes military history, bat exhibition, and infrared video observatory, while offering a panorama of the Montreuillois landscape.

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