Fort de Hollogne The Fort de Hollogne is one of twelve forts built as part of the fortifications of Liège in the late 19th century in Belgium . It was built between 1881 and 1884 according to the plans of General Henri Alexis Brialmont . Contrasting with the French forts built in the same era by Raymond Adolphe Séré de Rivières , the fort was built exclusively of unreinforced concrete , a new material , rather than masonry . The fort was heavily bombarded by German artillery in the Battle of Liège . Hollogne was never upgraded like the other forts of Liège and retains its character as a Brialmont fort . It is preserved as a museum and may be visited by the public . Description . The Fort de Hollogne is located about west of the center of Liège , directly adjacent to the Liège Airport ' s runway . The fort forms an isosceles triangle whose base is long and whose sides measure . A deep by ditch encircles the fort . The principal armament was concentrated in the central massif . The ditches were defended in enfilade by 57mm guns in casemates resembling counterscarp batteries , firing at shot traps at the other end of the ditch . It is one of the smaller forts of Liège . With the exception of the Fort de Loncin , the Belgian forts made little provision for the daily needs of their wartime garrisons , locating latrines , showers , kitchens and the morgue in the fort ' s counterscarp , a location that would be untenable in combat . This would have profound effects on the forts ' ability to endure a long assault . The service areas were placed directly opposite the barracks , which opened into the ditch in the rear of the fort ( i . e . , in the face towards Liège ) , with lesser protection than the two " salient " sides . The Brialmont forts placed a weaker side to the rear to allow for recapture by Belgian forces from the rear , and located the barracks and support facilities on this side , using the rear ditch for light and ventilation of living spaces . In combat heavy shellfire made the rear ditch untenable , and German forces were able to get between the forts and attack them from the rear . The Brialmont forts were designed to be protected from shellfire equaling their heaviest guns : 21 cm . The top of the central massif used of unreinforced concrete , while the caserne walls , judged to be less exposed , used . Under fire , the forts were damaged by 21 cm fire and could not withstand heavier artillery . Armament . Hollogne ' s armament included a Grüsonwerke turret with a single 21 cm gun , a15cm Creusot - Vanekerchove turret with twin guns and a 12 cm Châtillon - Commentry / Marcinelle et Couillet turret with two guns , all for distant targets . 57mm gun turrets were provided for local defense . The fort also mounted an observation turret with a searchlight . Seven rapid - fire 57mm Grüsonwerke guns were provided in casemates for the defense of the ditches and the postern , as well as in three turrets . The fort ' s heavy guns were German , typically Krupp , while the turret mechanisms were from a variety of sources . The fort was provided with signal lights to permit communication with the neighboring Fort de Loncin and Fort de Liers . The guns were fired using black powder rather than smokeless powder , producing choking gas in the confined firing spaces that spread throughout the fort . The fort was manned by 230 artillerymen and 120 infantry , commanded by Captain - Commandant Cuisinier . First World War . Liège first came under attack on 6 August 1914 . When the Liège ' s fortifications proved unexpectedly stubborn , the Germans brought heavy siege artillery to bombard the forts with shells far larger than they were designed to resist . Hollogne was heavily bombarded starting 13 May . On 15 May the neighboring Fort de Loncin exploded under bombardment at 1720 hours . At 1900 hours a German delegation arrived and offered to take the commandant to see the wreckage of Loncin . The fort ' s doctor and another officer went to Loncin , reporting back at 2200 . A plan was then proposed the evacuate and blow up the fort , which was stymied when the garrison discovered that it was surrounded . German artillery bombardment recommenced the next day ; Hologne surrendered at 0730 on the 16th , the next - to - last Liège fort to capitulate . Second World War . Hollogne was not upgraded in the 1930s as part of the Fortified Position of Liège , remaining essentially as it was built by Brialmont , with a few modifications by the 1914 - 1917 German occupiers . The Belgian Army used the fort to store munitions . In May 1940 the fort was bombed by Stuka s that had mistaken Hollogne for the active Fort de Flémalle . During the second occupation the fort was proposed as a launching site for V - 2 rockets . After the area was liberated in 1944 it was used by American forces as a hospital . Following the conclusion of the war it became a depot for Belgian forces , then became a Belgian Air Force command post until 1992 . It remained Ministry of Defense property until 1997 , when it was conveyed to the Ministry of Transport as airport property . Present . The fort has been restored by and is operated by the preservation organization " Comité de Sauvegarde du Patrimoine Historique du Fort de Hollogne " . It is open for public tours at stated times .