Fort de Chaudfontaine The Fort de Chaudfontaine , also called the Fort de la Rochette , 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 . The fort is now used as an adventure park . Description . The Fort de Chaudfontaine is located about southeast of the center of Liège , on the heights above the community of Chaudfontaine , overlooking the Vesdre valley . The fort was built as an irregular rectangle , in contrast to most Brialmont forts , which were triangular . 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 . The fort is one of the smaller Liège forts . 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 . Chaudfontaine ' s armament included a Grüsonwerke turret with a single 21 cm Krupp gun , a15cm Creusot turret with twin guns and a 12 cm Châtillon - Commentry turret with two Krupp guns , all for distant targets . Four Grüsonwerke 57mm gun turrets were provided for local defense . The fort also mounted an observation turret with a searchlight . Nine rapid - fire 57mm guns were provided in casemates for the defense of the ditches and the postern . 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 . 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 . Chaudfontaine was heavily bombarded starting 12 August , with firing rates of 200 to 300 shells per hour . On 13 August a shell hit the 21 cm turret , causing an explosion in the turret . The explosion , fire and the resulting toxic fumes killed at least 58 of the garrison . With the interior atmosphere unbreathable , the fort surrendered that day . Occupying the fort during the remainder of the war , Germans made a number of improvements to the fort in 1914 and 1915 . Fortified Position of Liège . Chaudfontaine ' s armament was upgraded in the 1930s to become part of the Fortified Position of Liège II , which was planned to deter a German incursion over the nearby border . The armament was upgraded with new guns in the turrets . This was accompanied by improvements to ventilation , protection , sanitary facilities , communications and electrical power . An air intake tower was added overlooking the Vesdre . New barracks were built at this time for peacetime accommodation . A large infantry shelter was constructed on the fort ' s glacis , intended to be linked to the main fort . Second World War . Chaudfontaine came under attack during the Battle of Belgium on 16 May 1940 . It was bombarded by the Luftwaffe in the early hours of the 17th , setting off explosions within the fort . A German attack in the daytime resulted in casualties among the garrison , and at 1930 hours the fort surrendered . Present . The fort de Chaudfontaine is occupied by an adventure park . A small cemetery and war memorial are located just outside the main gate , containing the bodies of the 71 killed in 1914 , including two from the Fort de Fléron , ten killed in the interval between the forts , and a civilian who was executed at Romsée .