The building of the Citadel was started immediately after the recapture of Calais by the Duke of Guise. The Seigneur de Gourdan had the castle, St. Nicholas church and an aristocratic district razed to the ground to make way for the fortress. The foundation stone was laid in 1560. Two gates give access through the enceinte, the Neptune gate to the east and the Boulogne gate to the south. Louis X111 and Richelieu, and later Louis X1V and Vauban all carried out improvements. During May 1940 the fortress was the scene of a keen resistance which is recalled by a plaque under the arch of the Boulogne gate. Another plaque at the Neptune gate is a memorial to the heroes of the 8th and 110th infantry regiments, to those who defended the fort in 1940, to young victims shot by the enemy in 1944 and to French sportsmen who died for their country. Since 1965 the fort has been the site of a Memorial Sportsground.

