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Fortification

Fort d'Ambleteuse

Ambleteuse, Opal Coast

About this place

Formerly mistakenly called “Fort Mahon,” the Fort d’Ambleteuse was built between 1682 and 1690 based on Vauban’s plans. Louis XIV had ordered its construction to protect the city.

It is referred to as a Napoleonic fort because it was restored and rearmed in 1802 by Napoleon.

The fort consists of an entrance courtyard, a casemate tower with a ring vault, an upper battery, a lower battery, and three levels of artillery emplacements. The Romans had already built a tower at this site, which was later converted by the English in 1544. This “castle of the seas” was a strategic location because, opening directly onto the English Channel, it was visible for miles around. This location made the fort impregnable.

Falling into ruin very quickly due to the elements and disuse, the fort was acquired by private individuals and restored. Abandoned and in ruins once again after the war, it was purchased in 1967 for a symbolic 1 franc by the association “Les amis du Fort d’Ambleteuse.”

Thanks to this effort, this historically designated monument is now open to visitors and awaits you, standing isolated on the banks of the Slack and its coastal dunes.

What to do nearby?

Upcoming events in Ambleteuse.

Festival 8 August → 9 August

Ambleteuse Celebrates the Sea and the Flobart

Ambleteuse

Ambleteuse celebrates the sea and the flobart on August 8, 2026. This celebration of maritime heritage brings together exhibitors showcasing flobarts, the traditional boats of the Opal Coast. The program features concerts and entertainment for all ages. You can also enjoy seafood dishes prepared by local restaurants. The event takes place in Ambleteuse. Admission is free.

Other places to discover

Fortification

Vauban Fortified Complex

Gravelines

Gravelines has preserved its entire bastioned wall, a fortress rebuilt in 1558 on top of a 14th-century medieval wall. This architectural gem is designated a “Historic Monument” within the grounds of the beautiful Porte aux Boules. A stroll along the rampart walk allows visitors to explore the 17th-century guardhouses, the cistern—whose vaulted chamber naturally stored and filtered water—and the Varennes and Uxelles barracks. The entire complex has been transformed into a cultural space, housing the Museum of Original Drawings and Prints and serving as the city’s cultural hub. A collection of contemporary sculptures by Charles Gadenne offers a poignant moment of emotion during the walk.
Fortification

Mimoyecques Fortress

Landrethun-le-Nord

A secret underground base from World War II designed by Hitler to house the V3 supergun aimed at London. A poignant memorial site that also serves as a preserved nature reserve.
Fortification

The Citadel

Calais

Built on the ruins of a medieval castle, the citadel is located at the northwest corner of the city (Avenue Pierre De Coubertin). It was Philippe le Hurperel, Count of Boulogne, who, in 1229, decided to build a medieval castle consisting of a square enclosure with six towers and a keep to protect the city. Initially inhabited by the counts of Boulogne and Artois, it later became a residence for the kings of England until 1558: Edward III resided there and fortified it for the first time. Since the medieval castle no longer met the needs of warfare, it was decided to build a citadel. Many houses were razed to make way for the construction site. Vauban (already known for Fort Nieulay) oversaw the restoration of the fortifications. Ultimately, the castle was completely destroyed in the 19th century. Visitors can still see the medieval ramparts, the emergency gate known as the “Porte de Boulogne,” and the Neptune Gate, also called the “Porte Royale.” Some of these gates have been designated as historic monuments, as have the moats and curtain walls. Today, the Citadel is surrounded by a neighborhood built in the regional style (red brick) dating from World War II and features a walking area and sports facilities. In fact, electric boats are available to cruise along the walls and explore the ruins in a different way. Now converted into a multi-sport and school stadium, the citadel features soccer fields, rugby fields, tennis courts, and more, allowing everyone to enjoy sports in a stunning historic setting.
Fortification

La Coupole

Helfaut

From November 1943 to March 1944, the Nazis began construction of the launch silo for the V2 rocket near Saint-Omer. This revolutionary secret weapon was developed by the Germans with the aim of destroying London and turning the tide of the war in their favor. Today, the dome serves as a history and memorial center chronicling a period of World War II: the space race, German secret weapons, and the German occupation of northern France... Thanks to historian Yves Le Maner, who oversaw the development of the historical program, you can relive the relationship between war and science, the Nazi system, the violence of the Blitzkrieg, the “gray” days of the occupation, the anonymous battles of the Resistance, as well as the joys and sorrows of liberation, through numerous exhibits such as films, documents, models, and eyewitness accounts. To construct the concrete dome, German engineers developed an innovative process that allowed for the rapid construction of this colossal structure. Using massive excavators, they drilled into the chalk on the surface of the plateau. Next, this mold was covered with earth to perfect its shape and reinforced with a strong steel framework. Then, the engineers poured concrete using pumps. Today, this 55,000-metric-ton structure has become a memorial, a testament to Nazi madness. Infrared audio guides (available in four languages: French, English, German, and Dutch) and video discs are at your disposal. Allow two and a half hours to explore this fascinating site at the heart of history and science. Don’t forget to stop by the gift shop, which offers books, souvenirs, and regional products.
Fortification

The Eperlecques Blockhouse

Éperlecques

Located on the edge of the Eperlecques Forest, this 22-meter-long blockhouse was originally intended for the launch of V2 rockets designed to destroy London during World War II. Between 1943 and 1944, more than 35,000 prisoners helped build the blockhouse, but during the 1943 bombings by the British “flying fortresses,” the project was repurposed, and the structure became a plant for producing liquid oxygen, intended to power the engines of a new generation of rockets. You’ll enter the blockhouse—designated a historic monument in 1985—through a 2-meter-thick reinforced door. The vastness of the halls and the jagged structures create an eerie atmosphere. During the tour, you’ll see terrifying “secret weapons” of the Third Reich and notice the thickness of the walls (5 meters). The upper slab, 7 meters thick, was raised using a system of jacks that lifted the roof as construction progressed, allowing the project to be completed while protecting the prisoners from bombing raids. The guided tour of this site and an audio tour (featuring documents, commentary, sound effects, etc.) presented inside the fortress will allow you to relive, with great emotion, the history of the structure, the technology behind the V2 rockets, and the construction techniques used for the bunker... all while allowing for a leisurely stroll through its parks. The site offers audio tracks and audio guides in 8 different languages, a visual guide in sign language, and is accessible to wheelchair users accompanied by an assistant.
Fortification

Fort Risban

Calais

Located on the coast, Fort Risban is one of the last coastal forts on French territory. Designated a historic monument in 1990, this fort was long a strategic stronghold for the city and has undergone numerous modifications since its construction during the Hundred Years’ War. In 1346, upon the arrival of the English in the Calais region, King Edward III decided to build a heavily armed wooden tower on top of Calais’s existing fortifications. The sole purpose of this was to prevent any supplies from entering from outside and thus to besiege the city through starvation. Having taken control of the city, the English replaced the wooden tower with a tall stone tower equipped with cannons, the Lancaster Tower. Situated on a sand spit, the fort was gradually separated from the dunes by ocean currents, eventually becoming entirely surrounded by the sea. After 1450, the Lancaster Tower took the name Risban and was enclosed by a polygonal wall that also included two other towers. In 1558, Risban returned to French control, and the governor of Calais decided to lower the height of the Lancaster Tower, which at the time posed a threat to the city. Two bastions were added, and in 1622, the fort served as the starting point for the construction of a seawall extending to Sangatte. In 1799, a gunpowder depot exploded, causing significant damage, but this did not prevent the fort from serving as the port’s main defense in the 1850s. During World War II, it sheltered many residents of Calais fleeing the bombings. Beginning in 1950, the fort’s ruins were opened to boaters; today, it serves as the headquarters of the Calais Yacht Club.

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