Siracourt V - 1 bunker The Siracourt V - 1 bunker is a Second World War bunker built in 1943 - 44 by the forces of Nazi Germany at Siracourt , a commune in the Pas - de - Calais department in the Nord - Pas - de - Calais region of France . Codenamed " " ( Waterworks St . Pol ) , it was intended for use as a bomb - proof storage facility and launch site for V - 1 flying bombs . However it never went into operation due to intensive Allied bombing that made it the most heavily attacked of all the German V - weapon sites . Background . With the Allies gaining air superiority by 1943 , different sections of the Luftwaffe – which had responsibility for the V - 1 – debated how best the weapons could be deployed in the face of an increased threat of aerial bombardment . The Luftwaffe ' s Flak division favoured dispersing V - 1s to a large number of small camouflaged launch sites . However , General Erhard Milch , who was in charge of the Luftwaffe ' s production programme , advocated large launch bunkers . Adolf Hitler was known to be in favour of such an approach , which had already led to the construction of a massive bunker at Watten for launching V - 2 missiles . In July 1943 , Luftwaffe chief Hermann Göring brokered a compromise under which both alternatives would be pursued ; four ( and ultimately ten ) heavy launch bunkers would be built along with 96 light installations . The heavy bunkers were all intended to be built to a standard design , codenamed " Wasserwerk " ( waterworks ) to conceal their true purpose . The first two would be built in the Pas - de - Calais at Desvres near Lottinghen and Siracourt near Saint - Pol - sur - Ternoise . The two sites are about and from London respectively . Two more would be built on the Cotentin Peninsula near Cherbourg . It was intended that all four would be operational by December 1943 , with further bunkers to be built subsequently . Design and construction . The Siracourt bunker is about long , wide and high , built using some 55 , 000 m³ of steel - reinforced concrete . Its design and method of construction took into account the lessons learned from the destruction in August 1943 of the Watten bunker while it was still under construction . It was constructed on high ground about a kilometer ( three - quarters of a mile ) north of the Hedin - Saint Pol road , to the north of the original site of the village of Siracourt . The bunker was built in loam y soil some deep , resting on a layer of chalk bedrock . The German engineers adopted a new method which they called " Verbunkerung " , which involved first building the roof flat on the ground then excavating beneath it – sheltered from bombs – to create the rest of the facility . The bunker would have been linked with the main railway line from Saint Pol to Abbeville , enabling trains carrying V - 1s and supplies to enter the body of the structure . It was , in effect , a fortified railway tunnel with a storage area capable of housing 150 missiles and an aperture from which they would have been launched . Although Allied reconstructions imagined a single launch ramp , it is possible that the Germans intended to install two parallel ramps to increase the rate at which V - 1s could be fired . Discovery and destruction . The Allies spotted the construction of the Siracourt bunker almost as soon as it began in September 1943 , when two parallel trenches were dug and concreted to form the walls of the structure . Heavy Allied bombing hindered construction but it continued until the end of June 1944 , when the site was wrecked by Tallboy bomb s dropped by the Royal Air Force . By this time about 90 per cent of the concrete had been completed , apart from the end sections , but the supposedly bomb - proof structure proved unable to withstand the six - ton Tallboy . One bomb fully penetrated the roof and exploded underneath , while another caused substantial damage when it exploded next to one of the walls . The ground around the site was churned up by over 5 , 000 tons of bombs . By the time the site was abandoned in April 1944 , the exterior had practically been completed but the excavation of the interior had only just begun . The Siracourt bunker is still extant today and is visible from the road . It is located on private land .