Fort Nieulay, located along the Avenue Pierre Coubertin, was originally dated to the 12th or 13th century. During the English invasion in 1346, sluices gates were added as water defences and a fort was built up around it in 1525 on the principle that the people of the fort could defend the town by flooding it. In April and May 1677, Louis XIV and Vauban visited Calais and ordered a complete rebuilding of Fort Nieulay. It was completed in 1679, with the purpose to protect the bridge of Nieulay crossing the Hames River. By 1815 the fort had fallen into a ruined state and it wasn't until 1903 that it was sold and improved by its farmer tenants. The fort was briefly the site of a low-key scuffle with Germans in May 1940.References:
The Château d'Olhain is probably the most famous castle of the Artois region. It is located in the middle of a lake which reflects its picturesque towers and curtain walls. It was also a major stronghold for the Artois in medieval times and testimony to the power of the Olhain family, first mentioned from the 12th century.
The existence of the castle was known early in the 13th century, but the present construction is largely the work of Jean de Nielles, who married Marie d’Olhain at the end of the 15th century.
The marriage of Alix Nielles to Jean de Berghes, Grand Veneur de France (master of hounds) to the King, meant the castle passed to this family, who kept it for more than 450 years. Once confiscated by Charles Quint, it suffered during the wars that ravaged the Artois. Besieged in 1641 by the French, it was partly demolished by the Spaniards in 1654, and finally blown-up and taken by the Dutch in 1710. Restored in 1830, it was abandoned after 1870, and sold by the last Prince of Berghes in 1900. There is also evidence that one of the castles occupants was related to Charles de Batz-Castelmore d'Artagnan, the person Alexandre Dumas based his Three Musketeers charictor d'Artagnan on.
During the World War I and World War II, the castle was requisitioned first by French troops, then Canadian and British soldiers. The current owner has restored the castle to its former glory.