Fort Eben - Emael Fort Eben - Emael ( ) is an inactive Belgian fortress located between Liège and Maastricht , on the Belgian - Dutch border , near the Albert Canal , and 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 successfully neutralized by glider - borne German troops ( 56 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 . Situation . 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 fortifications 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 no clearly defined perimeter , a lesson learned from the experiences of French and Belgian forts in World War I . The new Belgian forts , while more conservative in design than the French " ouvrages " , included several new features as a result of World War I experience . The gun turrets were less closely grouped . Reinforced concrete was used in place of plain mass concrete , and its placement was done with greater care to avoid weak joints between pours . Ventilation was greatly improved , magazines were deeply buried and protected , and sanitary facilities and general living arrangements for the troops were given careful attention . Eben - Emael and Battice featured 120mm and 75mm guns , giving the fort the ability to bombard targets across a wide area of the eastern Liège region . Eben - Emael occupies a large hill just to the east of Eben - Emael village , bordering the Albert Canal . The irregularly - shaped fort is about in the east - west dimension , and about in the north - south dimension . The fort was more heavily armed than any other fort in the PFL I . In contrast to the other forts whose main weapons were in turrets , Eben - Emael ' s main weapons were divided between turrets and casemate s . The 60mm , 75mm and 120mm guns were made by the Fonderie Royale des Canons de Belgique ( F . R . C . ) in the city of Liege . Underground galleries extend over beneath the hill , connecting the combat blocks and serving the underground barracks , power plant , ammunition magazines and other spaces . Fresh air was obtained from intake vents over the canal . Personnel . In 1940 Eben - Emael was commanded by Major Jottrand . There were around 1200 Belgian troops stationed at the fort , divided into three groups . The first group was permanently stationed at the fort and consisted of 200 men technical personnel ( doctors , cooks , weapon maintenance technicians etc . ) . The two other groups consisted of 500 artillerists each . In peace time one group would be stationed at the fort for one week . The other group would be in reserve at the village of Wonck , about 5 km away . These two groups would switch places every week . Except for some of the officers and NCOs , most of the men were conscripts . The majority of these were reservists and were called up after the Invasion of Poland in 1939 . Infantry training was poor , since the men were considered purely as artillerists . 1940 . On 10 May 1940 , 78 paratroopers of the German 7th " Flieger " ( later 1st " Fallschirmjäger " Division ) landed on the fortress with gliders ( type DFS 230 ) , armed with special high explosives to attack the fortress and its guns . Most of the fort ' s defenses were lightly manned and taken by complete surprise . Much of the fort ' s defensive armament was destroyed in a few minutes . The attackers were unable to penetrate inside the underground galleries , but the garrison was unable to dislodge them from the surface of the fort . The fortress surrendered one day later , when the German paratroopers were reinforced by the German 151st Infantry Regiment . While 1200 soldiers were authorized to be at the fort on any given day , only 650 were at the fort with an additional 233 soldiers 6 km away at the time of the German assault . However , the Germans had planned the capture of the fort well in advance . In preparation they had practiced assaulting a full - scale mock up of the fort ' s exterior in occupied Czechoslovakia using the recently built and captured border fortifications that were modeled to a large degree on western designs . Adolf Hitler himself conceived of a plan to take over the fort by getting men on the fort by using gliders to overcome the problem of concentrating an airdrop on a small target , and utilizing the new top secret shaped charge ( also called " hollow charge " ) bombs to penetrate the cupolas . Good espionage and superior planning , combined with unpreparedness on the Belgian side , helped make the execution of Hitler ' s top secret plan a swift and overwhelming success . The capture of Eben - Emael involved the first utilization of gliders for the initial attack and the first use of hollow charge devices in war . The gliders , led by First Lieutenant Rudolf Witzig , landed on the roof of the fortress and being totally silent took the defenders by complete surprise . There they were able to use the hollow charges to destroy or disable the gun cupolas . They also used a flamethrower against machine guns . The Belgians did destroy one of the key bridges , preventing it from being used by the Germans but also preventing a relieving force from aiding the fortress . The Germans lost only 6 of the assaulting engineers and had 21 wounded , keeping pinned all the defenders until the arrival of the main attacking army . After the extraordinary success in the capture of the fort , Hitler personally decorated all the participants in the assault . Eben Emael , considered the strongest fortress in the world , was the linchpin of the Belgian main line of defense and dominated all terrestrial communications around the Albert Canal . It was a sensational coup and its loss delivered a hard blow from which the Belgian Army could not recover . Present day . Fort Eben - Emael is now open for the public to visit . While still military property , it is administered by the Association Fort Eben - Emael , which provides tours and activities .