Weingut I In 1944 the Third Reich began work on the construction of a partially underground bunker factory codenamed Weingut I ( English : Vineyard I ) in the forest known as the , slightly to the west of Mühldorf am Inn in Upper Bavaria . Plans for the bunker called for a massive reinforced concrete barrel vault composed of 12 arch sections under which Messerschmitt Me 262 jet engines would be manufactured in a 9 - storey factory . Upon completion these were to be sent to a similar installation in the area of Landsberg am Lech ( codename Weingut II ) , where the final assembly of the planes was to take place . This network of underground factories was intended to ensure the production of the Me 262 at a time when the Allies had already gained control of the German airspace . Despite it being increasingly clear to the organisers of the project that it would never be finished in time to make a difference in the war , the construction of Weingut I was approved on a 6 month time - line . Of a total of 10 , 000 workers who worked on the project , 8 , 500 were forced laborers and inmates of the Mühldorf concentration camp network . Of these more than 3 , 000 would die of overwork , underfeeding , and SS brutality . By the war ' s end , only 7 of the planned total of 12 bunker sections had been built , and construction of the factory itself had not begun . After the liberation of the area and its associated camps in May 1945 , control of the construction site fell to the US Army , which made extensive studies of its innovative construction techniques before demolishing all but one section of the main bunker in 1947 . Today the bunker grounds are a listed monument . Occasional tours of the site are offered by a Catholic nonprofit group in Mühldorf . Background . In early 1944 , the Allied air war began to focus primarily upon the destruction of the Luftwaffe in preparation for the invasion of Normandy . Plans for the so - called " Big Week " , which was intended to permanently smash the German capacity to produce fighter aircraft through targeted airstrikes on final assembly factories , were already underway in 1943 . Between February 20 – 25 , 1944 , approximately 10 , 000 American and British aircraft , including about 6 , 000 bombers , attacked strategic targets all over Germany . Following these attacks , which seriously damaged German aircraft production , the production quota fell drastically . In response the ( Fighter Staff ) was founded in March 1944 with the task of ensuring the preservation and growth of fighter aircraft production . It superseded the Ministry of Aviation in this jurisdiction . At the head of the Jägerstab was armaments minister Albert Speer , as Deputy the Secretary of State Erhard Milch , as Chief of Staff Karl Saur . Their plan to protect the aircraft industry , especially the manufacture of the jet - powered Messerschmitt Me 262 , entailed the relocation of assembly plants into underground bunkers . This idea was not entirely new , as a similar ( but never realized ) proposal had already been considered in October 1943 . The Jägerstab ' s plan included six locations in which partially underground bunkers were to be built , and at first called for the bunkers to be encompass a minimum area of 600 , 000 to 800 , 000 m² apiece . However , by the time of the Jägerstab meeting of 17 March 1944 , the projected size of the each building had sunk to 60 , 000 m² . By June 1944 the invasion of the allies had forced the Jägerstab to focus in the end on two locations in Upper Bavaria . Three bunkers were to be built at Kaufering in the Landsberg am Lech district under the codename " Ringeltaube " ( Common Wood Pigeon ) , while the codename " Weingut I " ( Vineyard I ) was chosen for the factory in the . According to the testimony of Franz Xaver Dorsch , who was responsible for the construction , the fighter factory would be completed in five to six months at best . Speer later wrote in his memoirs that at the time it was already not difficult to foresee that the project would not be completed within the planned time . The location in the area of Mühldorf fulfilled all of the important requirements . There was an adequately solid gravel bed beneath the terrace of the Inn and the water table was adequately deep . Strategically the important railway juncture of Mühldorf was advantageous , and the wide - ranging forest of the Mühldorfer Hart would offer excellent camouflage for the completed bunker . Construction . Management . The chief construction office of Organisation Todt ( OT ) in Berlin , and therefore Speer ' s deputy in the OT Franz Xaver Dorsch , was responsible for the planning and organization of the project . On site the " OT - Einsatzgruppe Deutschland VI " ( OT - Task Force Germany VI ) supervised the construction from their offices in Ampfing , Mettenheim and Ecksberg at Mühldorf . Architect Bruno Hofmann was the " OT Oberbauleiter " ( Chief Construction Leader ) . The technical aspects of the construction were assigned to the company ( P & Z ) . Other companies worked on the project as subcontractor s . P & Z had already been active in the area of Mühldorf in the 1920s , with the building of the Inn Canal . Almost 200 employees of the company were sent to Mühldorf for the project , were they operated as the OT unit " Polensky & Zöllner , Bautrupp 773 " . The P & Z leader at the construction site was the engineer Karl Gickeleiter . The cost of the project has been estimated at almost 26 million Reichsmarks . Workforce . A huge workforce was necessary for the construction project . P & Z used a total of 200 of its own workers , about 800 to 1000 workers from their affiliated Soviet companies , and 200 to 300 Italian workers . This group of about 1 , 500 was vastly inadequate if the project was to be completed on schedule . Therefore it was decided that forced labor would be employed , as was common under the Nazis for projects of this magnitude . A large portion of the forced workers were prisoners of the Mühldorf concentration camp . Further labor camps were built by the OT to house them in the Mühldorfer Hart , Ampfing , Mettenheim and Ecksberg . A large number of Soviet prisoners of war also made up the forced laborers . Overall more than 10 , 000 workers were assigned to the Weingut I construction site . As a rule two shifts of 4 , 000 men apiece worked on the project . According to the records of P & Z the POWs worked a total of 322 , 513 hours ; the concentration camp prisoners , 2 , 831 , 974 . The company was paid 1 , 892 , 656 . 20 Reichsmarks by the SS and the OT . Preparations . Adolf Hitler ' s orders of 21 April 1944 gave official approval for the commencement of work on the structure . Next the necessary ground for the project was confiscated without compensation . Around the middle of May the OT established its offices in the Ecksberg Foundation ' s ( Stiftung Ecksberg ) building complex . The Ecksberg Foundation , a home for the mentally ill , had been taken over by the state in 1938 . It was uninhabited by this time , as the Nazis had soon thereafter murdered some 248 to 342 of those in the foundation ' s care . At the same time the OT erected its first barracks camp . Afterward the required construction machinery was little by little supplied to Mühldorf . The equipment had to be brought together from sources throughout the Reich and its occupied territories , which was an especially complicated endeavor given the military situation . Nonetheless a concrete factory , a carpentry shop , a gravel sorting plant and further facilities had to be built . Besides these additional smaller bunkers intended to serve as air raid shelters were erected before construction on the main site began . For the transportation of material to and from the site the Reichsbahn laid down a network of siding that was connected to the Munich - Mühldorf line . Upon completion the entire bunker was to be covered with soil and planted over with trees and bushes , but considering the scale of the project it was hardly possible to effectively camouflage it from aerial reconnaissance during the construction process . Efforts to that effect were therefore not especially thorough . Indeed the site was hard to miss , and the USAF took several aerial photos of it in February 1945 during reconnaissance prior to the bombardment of the airfield at Mettenheim and the train yard at Mühldorf . The site was discovered upon examination of the photos , as an overhead view of main bunker drawn in March 1945 and labeled " MUHLDORF ( GERMANY ) SEMI - BURIED INSTALLATION " attests . The site was never bombed , however . The reasons why are unclear . One reason could be that the existence of the work camp was known and that the Allies did not want to risk bombing it by accident . It may also have been known that its completion was unlikely and thus other targets presented a higher priority . Process . The actual work on Weingut I began in July 1944 . According to plans , the bunker would be made up of 12 arches stretching east to west in a barrel vault 400 meters long and 85 meters wide . The arches would have an internal height of 32 . 2 m , 19 . 2 m of which was under the ground level . Their thickness reached 3 meters , and would have eventually reached 5 meters through a further concrete pour . For the building of the bunker an effective and simple new procedure was employed . First an underground " extraction tunnel " , fitted with a single train track and a gated roof , was built along the entire length of the planned bunker . Next the foundations for the abutments , which were up to 17 m thick , were dug . The gravel extracted from the foundations was piled up between the foundations to support the arches while they were being built , essentially serving as formwork instead of traditional wooden scaffolding . As each arch was completed , the gravel beneath it was dug out and dumped through the gates of the extraction tunnel into waiting mine carts , which would then be taken away . When the tunnel had been completely uncovered it would be disassembled and backhoes would continue the excavation to a depth of 19 . 2 meters . Starting from the east , one arch after another was erected in this way . Eight floors were to be erected beneath the arches , but this was only begun with the first arch . By the end of April 1945 only seven of the projected twelve arches were completed . In the last months of the war it was no longer possible to obtain the necessary materials and workers in order to stay on schedule . War ' s end and afterward . Liberation and demolition . When the 47th tank battalion of the 14th Armored Division reached Mühldorf in the early days of May 1945 , the construction area and all related facilities were placed under US military administration . The company was allowed to dismantle and remove its construction equipment , and the Reichsbahn took up the tracks that led to the complex . Next the army decided to use the grounds as a bomb test site in order to determine the effectiveness of the bunker : This proposal was accepted and in the summer of 1947 the command for the demolition was issued . 125 tonnes of TNT were used for the demolition , which destroyed six of the seven completed arches and damaged the seventh . Trial . After the war the US Army ' s Dachau Military Tribunal prosecuted perpetrators of war crimes in connection with the Weingut I project and the associated concentration and labor camps in the , which was one of the Dachau Trials . Among the accused were members of Polensky & Zöllner ' s administration , including Karl Bachmann , Director of the Munich branch of P & Z ; Karl Gickeleiter , who oversaw construction at the main site ; and Otto Sperling , construction foreman . The sentencing was performed on 13 May 1947 . The charges against Karl Bachmann were dropped , as his involvement in the maltreatment of the prisoners could not be proven . Gickeleiter was sentenced to a 20 year prison term , which would be reduced to 10 years in 1951 before he was released early on 19 July 1952 . The death sentence against Sperling was shortly thereafter shortened to life imprisonment and later reduced even further before he was finally released on 20 July 1957 . 1980s to today . The ruins of the bunker complex can still be seen in the woods near Mettenheim , although much material from the site has been scavenged in the intervening years by local companies for other building projects . The grounds entered the public eye again in the 1980s , when rumors began to circulate that chemical agents of the Wehrmacht had been stored in the tunnels of the complex after the war . This was not confirmed by the authorities until 1987 ; the chemicals , including CLARK 2 , were subsequently removed . In 1992 , the " Bundesvermögensverwaltung " ( Federal Property Administration , an agency that has since been superseded by the " Bundesanstalt für Immobilienaufgaben " ) proposed to demolish the bunker . Although the communities of Mettenheim and Ampfing endorsed the demolition , many others opposed the proposal , and it was rejected by the government of Upper Bavaria . In the meantime the bunker grounds had been added to the Bavarian list of monuments as a memorial to the victims of Nazi atrocities . Today the Mühldorf District Catholic Education Center ( Katholische Kreisbildungswerk Mühldorf ) administers occasional tours of the bunker grounds and the and the former concentration camp .