- Fort, citadel and fortification
In 1656, Vauban redeveloped the Philippeville Fortress on Louis XIV's request. He strengthened the site's defences, emphasising its star shape. Part of the underground network created then remains and can be visited.
These galleries, 10 km long and 2 m wide are located 10 to 15 metres underground. Entirely built by hand from the region’s stone, they have rounded ceilings. They were used to connect the guard posts outside the main building to the Philippeville stronghold.
While only 1 km is accessible to the visitors at present, requests have been made to extend the tour further.