Fort Eben-Emael (, ) is an inactive Belgian fortress located between Liège and Maastricht, on the Belgian-Dutch border, near the Albert Canal, outside the village of Ében-Émael. It was designed to defend Belgium from a German attack across the narrow belt of Dutch territory in the region. Constructed in 1931–1935, it was reputed to be impregnable and at the time, the largest in the world. The fort was neutralized by glider-borne German troops (85 men) on 10 May 1940 during the Second World War. The action cleared the way for German ground forces to enter Belgium, unhindered by fire from Eben-Emael. Still the property of the Belgian Army, the fort has been preserved and may be visited. Location The fort is located along the Albert Canal where it runs through a deep cutting at the junction of the Belgian, Dutch and German borders, about northeast of Liège and about south of Maastricht. A huge excavation project was carried out in the 1920s to create the Caster cutting through Mount Saint Peter to keep the canal in Belgian territory. This created a natural defensive barrier that was augmented by the fort, at a location that had been recommended by Brialmont in the 19th century. Eben-Emael was the largest of four forts built in the 1930s as the Fortified Position of Liège I (Position Fortifiée de Liège I (PFL I)). From north to south, the new forts were Eben-Emael, Fort d'Aubin-Neufchâteau, Fort de Battice and Fort de Tancrémont. Tancrémont and Aubin-Neufchâteau are smaller than Eben-Emael and Battice. Several of the 19th century forts designed by General Henri Alexis Brialmont that encircled Liège were reconstructed and designated PFL II. A great deal of the fort's excavation work was carried out on the canal side, sheltered from view and a convenient location to load excavated spoil into barges to be taken away economically. The fort's elevation above the canal also allowed for efficient interior drainage, making Eben-Emael drier than many of its sister fortifications. Description Fort Eben-Emael was a greatly enlarged development of the original Belgian defence works designed by General Henri Alexis Brialmont before World War I. Even in its larger form, the fort comprised a relatively compact ensemble of gun turrets and observation posts, surrounded by a defended ditch. This was in contrast with French thinking for the contemporary Maginot Line fortifications, which were based on the dispersed fort palmé concept, with