​​Fort Nieulay, located west of Calais near the Guînes River, originated as a 16th-century flood fortification. Initially constructed by the English in 1525, it featured a square layout with towers at each corner and thick walls accommodating around twenty soldiers. Captured by the French in 1558 and later occupied by the Spanish in 1596, the fort underwent successive modifications including the addition of parapets, bastions, and changes to the original towers.

​In 1627, under Cardinal Richelieu, the structure was remodelled and linked by bridge to a hornwork. Later visits by Louis XIV and military engineer Vauban led to the construction of a new fortification slightly further west, better suited to protect the sluices essential for flooding the approaches to Calais. Three sluices were housed within the fort, regulating the flow of local waters and seawater. The internal layout included barracks, a chapel, storehouses, and a cistern, while each of the two gates was protected by a ravelin.

​By the late 17th century, changes to the local waterways rendered the sluices obsolete. The fort rapidly deteriorated, was stripped of materials during the 19th century, and lost its strategic importance. Decommissioned in 1903, it was sold and later rented to local farmers.

​During the German invasion in 1940, Fort Nieulay was again a site of combat. Defended by French and British forces, including Sergeant Henneton and Captain Munby, it was attacked by the German 10th Panzer Division under General Schaal. The Germans subsequently fortified the site, designating it Stützpunkt 88 Glan. The fort was equipped with bunkers (types L 408, R622, R600b, and R680), machine-gun positions, anti-tank weapons including a 7.5 cm Pak 40, and served as headquarters for the Reserve Flak Abteilung 253.

​In 1944, Fort Nieulay was retaken by Canadian forces, specifically the Royal Winnipeg Rifles, following intense fighting. Post-war, it was used as a quarry, leading to structural collapses. Now owned by the city of Calais, parts of the site—including the powder magazine, officer’s quarters, and fort walls—have been restored. A commemorative plaque at the entrance honours the defenders of 1940 and the liberators of 1944.