In June 1939, a group of Kriegsmarine technicians set out into countryside outside of Bernau – a good 20 kilometers north of Berlin – armed with a mobile radio truck. The Navy Technicians were carrying out a series of radio tests in the area, which judging by the commotion that set in later that year, proved to be quite successful.
Construction of the Lager Koralle
By the end of 1939, the Kriegsmarine acquired 54 hectares worth of land in Lobetal and promptly erected a two-meter-high, barbed wire topped fence around their new piece of land. Endless rows of trucks started moving material in from Bernau to begin with the construction of what the locals erroneously called a “Marineschule” – a Navy academy.
Shortly after, four 80-meter-high – interconnected masts sprung up in the middle of the “restricted” zone. It turned out that the Lobetal area was perfectly situated for a military facility to send and receive radio signals to and from the German Navy, as well as still being logistically close to Berlin.
Essentially, they were building the secret bunker complex for the German Navy Command (the Luftwaffe had the Bunkeranlage Kurfürst in Potsdam and the Lager Robinson in the Rominter Heide, while the Oberkommando des Heeres and the Oberkommando der Wehrmacht had the Nachrichtenzentrale Zeppelin in Wünsdorf also known as the Bunker Zeppelin).
East German additions to the area around the Lager Koralle. Bottom picture is one of the original fire ponds.
While the construction of what would later be known as Lager Koralle is most associated with Grand Admiral Karl Dönitz, it was his predecessor Großadmiral Erich Raeder who was responsible for the construction and development of the secretive navy complex.
Of course, the local landowners protested against the (forced) sale of their land, but if the Nazi regime wanted something, it definitely got its way. The Kriegsmarine argued that setting out to look for a new patch of land and doing all the technical tests again would only create an unnecessary delay in what was deemed to be a project of strategic importance.
Interestingly enough, one of the areas that the Kriegsmarine had previously scouted was at the nearby Bogensee – though this plan had to be abandoned as the land was already given to Reichspropagandaminister Joseph Goebbels.
The Oberkommando des Heeres and the Reichspostsministerium already had experience with over ground communication bunkers – having previously constructed the Zeppelin, Maybach I and II – which housed the High Command of the Army and the Supreme Command of the Armed Forces – so it was natural that the Reichspost was tasked again with the construction of a similar complex.
While plans for a new Führungsstelle der Seekriegsleitung (Headquarters of the Maritime Warfare Command) outside of Berlin were already set in motion, the High Command of the Navy (OKM) only really decided at the end of 1939 on the construction of a so called Draht-Nachrichtenbunkers similar to those in Zossen. The OKM had initially planned for the 1st of April 1941 as the finished construction date, but the Reichspost dismissed this as unrealistic and suggested that October of the same year would be more viable.
By the end of June 1940, the Oberkommando der Marine blinded by the successful events of the war, ordered that the construction of the Draht-Nachrichtenbunkers be suspended, while work on a smaller communications bunker would be continued.
Despite this, work still continued at the Lager Koralle, with cable connections and other buildings being constructed.
Großadmiral Dönitz moves in
The “Befehlshaber der Unterseeboote” – in short B.d.U (The Commander of the Submarines) was initially stationed in Wilhelmshaven (Germany), but after the occupation of France was moved first to Lorient and then to Paris (after British Commandos and the Royal Navy Launched Operation Chariot on the 28th of March 1942). After being promoted to Großadmiral and designated as the Oberbefehlshaber der Marine (Ob.d.M – Commander-in-Chief of the Navy) in 1943, Großadmiral Dönitz moved his headquarters back to Berlin.
It is clear that during the construction of the Lager Koralle, extensive use of forced and slave labor was used. The Organisation Todt was involved with the construction which relied heavily on prisoners of war and forced laborer’s from occupied countries and territories.
Its worth mentioning that the Lager Koralle – aside from being a bomb proof secret headquarters for the Oberkommando der Kriegsmarine – was also the main transmission base for the Nazi U-Boot fleet. Its important to point out though that the Lager Koralle from a radio communication and operational point of view was only a receiving station, meaning that they only directly received transmissions.
All transmissions that went out from the Lager Koralle were actually sent through separated transmission systems. i.e remote controlled from stations further away (roughly 20km) through encrypted Morse Code that were connected to the Koralle via cable lines. The reason for this (which is still valid today) is that the sending station would have interfered with the delicate reception systems.
The Lager Koralle was completed (from an operational perspective) by the end of 1942. The Oberkommando der Marine (which was located at the Tierpitzufer 38–42, now Reichpietschufer 72–76) sustained heavy damage after a bombing raid on the 22nd of November 1943 – which prompted the Ob.d.M and the Seekriegsleitung to move to the Lager Koralle and the “Ausweichstelle Bismarck” in Eberswalde.
At this point the Lager Koralle consisted of
- A Hochbunker
- A Lagezimmerbunker
- The Fernmeldebunker with a single story building atop
- Barracks for the military personel
- Baracks for the Female Marinehelferinen
- An officers casino, also known as the Villa Dönitz
- Service Buildings
- and several fire ponds
At its peak, over 1000 people were employed in and around the complex.
The Lagezimmerbunker had capacity for 70 people, while the underground bunker of the Funkempfangsgebäude could hold up to 130 people, and the Air Raid bunker had capacity for 750 people. The Luftwaffe flew continuous inspection flights over the area and gave detailed reports concerning the state of camouflage, suspicious shadows, and ordering the removal of so called “desire paths” between barracks.
In addition to the already existing hydrant system – so called fire ponds were to be erected. But the German military being the German military – the architects had the orders to avoid regular shapes, and were under strict orders to make sure the fire ponds were all different from each other (as to avoid detection/suspicion by allied reconnaissance flights).
After the war, rumors started creeping up that the fire ponds were actually depictions of the seven seas and that Dönitz and his admirals would use them to simulate navy battles, which of course was completely untrue.
Entrance to the Lagezimmerbunker. You can clearly tell apart the original structure and the GDR additions.
By late march, the Lager Koralle was only maned by Dönitz and a skeleton crew. Most of the other staff had already moved on to other Navy Intelligence locations, but Dönitz wanted to stay as long as possible to keep in contact with Hitler. Dönitz and his staff moved out of the Lager Koralle into a mobile (train) headquarters called “Auerhan” (also known as a Sonderzug or Führersonderzug) northwest of Berlin but moved back to the Koralle relatively quick due to the advancing Russian front.
An Air Raid hit the command bunker on the 17th of April, and the Soviets had reached the perimeter by 21st. The remaining Navy soldiers and a group of pioneers tried to destroy the bunkers and the U-boot diesel generators by throwing hand grenades and explosives into the bunkers, as well as blowing up the antennas. After that they headed towards Berlin for the endkampf.
Dönitz and his wife left the lager Koralle on the 22nd of April to the “Objekt Forelle” in Plön (also known as “Krokodil”) – which was the designated alternative Navy Communications Headquarters. They didn’t stay long in Plön though, as they moved to Flensburg-Mürwik. on the 1st of May 1945, where the infamous “Regierung Dönitz” had its last stand.
The Soviets and the East Germans move into the Koralle
The Soviet Red Army took over the Lager Koralle on the 22nd of April 1945, and began demolishing (aka blowing up) the Hochbunker and the Lagebunker with old mines and leftover explosives (which still contaminate the ground today). Over the coming weeks and months, almost all buildings were torn down aside from the Officers Casino, a Garage, the Bath House and the ruin of the Funkempfangsgebäude.
The Soviets had also attempted to destroy the bunker underneath and but only managed to do so partially. The explosion managed to destroy a relative thin (25cm) false ceiling, partially destroy the 1m thick bunker ceiling and destroy large parts of the of the Funkempfangsgebäude.
On the roof of the former Lagezimmerbunker
The locals plundered the ruins as best they could, and the rest of the salvageable technical equipment and building material was shipped off to the Soviet Union as war reparations.
The Interior Ministry of the GDR acquired large swathes of the Lager Koralle in the early 1950s and began removing the leftover munitions and demolished the ruins of the Funkempfangsgebäude. The area was then used by East German Police Units, specifically the 17th, 18th and 19th Volkspolizei to train in urban warfare tactics.
The aforementioned fire pond was kept, and a new container building was set up, and some new barracks were constructed to house the units. The Villa Dönitz which had survived the war unscathed was converted into an orphanage for East Prussian refugees around 1948.
Top left image shows the former internal staircase of the Lagezimmerbunker.
It’s not exactly clear when or why Group of Soviet Occupation Forces in Germany began showing interest in the remaining underground bunker underneath the former Hauptfunkgebäude, but by the mid 1950s, the red army began extensive clean up and restoration work. By that point it was converted into an underground munitions bunker.
In the early 1970s, specialists of the 20th Guards Army (which was already heavily deployed in the area around Eberswalde) converted the bunker into Command Message Center. The former Submarine Command Communications bunker had now been reconverted into a similar use – but now it was being used so Moscow could keep in contact with its forces that were stationed around the GDR.
With the NVA, East German Police (including telecommunication units from the Ministry) and the Red Army all hanging around the same area, rumors of course came up about the secretive nature of the area. Some of these rumors (which still exists to this day) include statements like: the fact that the entire area had bunkers underneath, that the Soviets hollowed out entire mountains, and that they converted the bunkers and made them 5 stories deep.
One of the most interesting – if albeit most unlikely – rumors to surface was that the Nazis had apparently (when constructing one of the bunkers) assembled a submarine in the lowest floor and then flooded it (the floor, not the submarine). New submarine commanders and their crews then had to then absolve their training there.
Only the bunker is left of the Funkempfangsgebäude today – which to a large extent still remains in its original German design. Originally, the Funkempfangsstelle or Funkempfangsgebäude was constructed as the main receiving and sending station. There was a large single story building which housed two radio rooms, a decryption room, a workshop and the office of the Kommandant.
The building had direct telephone connections to all sending stations, as well as to the stations in Lorient and Paris. Underneath the one story building was a two story bunker, which was equally equipped with generators and other radio and technical equipment. As the war went on, most of the high ranking staff moved over into the safer Lagezimmerbunker, while the remaining staff was moved into Bunker of the Funkempfangsstelle.
The entrance to the Soviet portion of the Lager Koralle
The buildings that can still be found today above ground are to 99% of soviet origin, an attempt to disguise what was underneath. The bunker under the Funkempfangsgebäude consists of two floors. The first floor had a ceiling height of 2,30m while the second floor had a ceiling height of roughly 1,80m. After the Soviets moved in, they fitted the first floor with technical operation rooms, a command center, weapons storage, kitchen, mess hall, toilets, the electricity generators and the emergency exit. The second floor had the water supply, heating and ventilation system – and of course a sauna.
Ventilation chimney of the Funkempfangsgebäudebunker and entrance to the bunker. *Note: The Plotbot Ken Graffiti is not the one referenced further down below.
It’s worth mentioning that even by 1940s standards, the Bunker was only really able to withstand any bombardment due to the added protection of the Funkempfangsgebäude above it. After the Soviets had removed the Funkempfangsgebäude, the bunker had a relatively weak protection. For reasons that be, the Soviets never bothered increasing the ceiling thickness or even just adding more earth above the structure.
Whats left of the Soviet buildings
When it came to laying new cables, the Soviets also didn’t bother using existing or creating new cable canals, but instead just simply laid them 40cm deep in the earth. Secure and tamperproof this was not. The Soviets also never really bothered properly converting the bunker so it would be safe against biological or chemical weapons, and it gave off the impression that they never intended it to be used as a command post if a war ever broke out.
The Lagezimmerbunker can be found roughly 200m away from the Funkempfangsgebäude Bunker and was constructed as a two story Hochbunker – though the lower floor was located partially underground when they moved more earth in after construction was completed. The Lagebunker is often erroneously called a Flak Bunker as it had 3 AA canons fixed on the roof.
While it’s not entirely clear if the AA canons were an afterthought or had always been planned – they do not appear in the original plans of the Lagezimmerbunker. What also gives the impression that the AA Guns were more of an “afterthought” was that the ceiling width was increased from 2,50m to 3,50m.
The Lagezimmerbunker Bunker – or War Room Bunker was built with offices for the Oberbefehlshaber der Marine, the Seekriegsleitung and other high-ranking officers, as well as telecommunication rooms, meeting rooms and the Lagezimmer – the war room – which gave bunker its name. An attempt to demolish the Lagezimmerbunker was undertaken sometime in mid 1945.
While a large quantity of explosives was used, it doesn’t appear to have been a very precise effort. The explosion caused the intermediate ceiling to collapse, and pushed the walls to the side. The force of the explosion caused the ceiling to lift off the walls and come back crashing down, cracking it.
Other parts of the bunker remained relatively intact and no further attempt was made to demolish the ruins. As previously mentioned, the Volkspolizei and Betriebskampfgruppen (a paramilitary organization comprised of loyal working class people) used the ruins to train military tactics and performed some slight modification on the ruins.
The Luftschutzbunker – just like the Lagezimmerbunker of the Lager Koralle was built as a Hochbunker, though all of its floor were located above ground. It was constructed to keep around 750 people safe during air raids, though its location is somewhat of a mystery as it wasn’t constructed centrally, but more off to the southern edge of the Lager Koralle.
Remnants of the former side entrance to the Luftschutzbunker
All original plans had been destroyed during the war (and no single Hochbunker built by the Germans had the same design), so it’s hard to say exactly what the original layout of the Luftschutzbunker was. What we do know is that it had three above ground floors, and two entrances – one to the east and one to the west.
The entrances had pressure doors and were constructed in such a way that the pressure of an exploding bomb would break when it hit the lock and corridors. Like the Lagezimmerbunker, the Luftschutzbunker was demolished around mid to late 1945, with at least 1 explosion, and they used leftover munitions for at least one of these detonations. The unexploded evidence can still occasionally be found scattered in the area.
The entrances survived the detonation relatively unscathed, but the main core of the bunker was completely destroyed. The ceiling burst into multiple sections and was essentially scattered around the bunker. The damage to the interior was so great, that it’s impossible to even guess what the interior layout of the bunker originally looked like. If you do crawl into the entrance, you’ll be able to spot one of the only surviving original German inscriptions from the Lager Koralle:
Der aufenthalt in den Gängen ist verboten!
It is forbidden to stay in the corridors!
Evidence can be found here as well of treasure hunters, digging underneath, looking for tunnels and secret entrances. Not only is this extremely dangerous but also incredibly stupid. Enough surveys of the area have been done to prove that there’s nothing there.
The Villa Dönitz
The Officers Casino – also known as the Villa Dönitz was most likely built around 1942, or early 1943. Both Großadmiral Dönitz and his wife lived here until they evacuated to Plön on the 22nd of April 1945. The Villa Dönitz survived over the years, initially as an orphanage for east Prussian children. An additional second story was added to the building in 1968. Today a so-called hippy commune uses the buildings and the nearby field to grow organic produce (and apparently, they tend to the filed without the help of any industrial machines).
The Villa Dönitz. If you look closely, you can tell the difference between the original ground floor and the second floor that was added in the late 1960’s.
When the Soviets moved out of the Lager Koralle, they handed it back over to the German state which – as with so many former Nazi turned Soviet Military installations – had no military use for it. The technology was outdated and the cost of refurbishing and modernizing these installations outweighed any benefit they might have had.
The Lager Koralle today
The areas with the Lagezimmerbunker and the Luftschutzbunker as essentially publicly accessible – but the Fernmeldebunker and the area around are still managed by the Brandenburgische Boden-Gesellschaft under the authority of the State of Brandenburg. Over the years, vandals and idiots have made their way into the bunker – more often than not with force, damaging the entrance, ripping out cables and stealing leftover technical equipment.
A group of military and radio historians have spent that past decade (and more) exploring, documenting and caring for the area and have legal access to the Lager Koralle. They are continuously working on gaining as much knowledge about the Lager Koralle as well as getting funding and possible monument heritage protection for the area.
Some of the German-Russian handover documents of the Lager Koralle from 1992
Sadly, the vandalism hasn’t stopped – and as recently as September 2020, I’ve seen reports and photos of idiots vandalizing the Fernmeldebunker (among them a somewhat well-known graffiti artist). It’s truly a shame, as these actions make it more difficult for legitimate and legal visits to take place in the future, and threaten the entire project.
The majority of what’s left of the Lager Koralle can be visited legally and without the need for any tours as its public property. Extreme caution is advised especially in the summer as the as the forests surrounding the ruins are a maximum fire risk.
The bunker ruins aren’t meant for climbing either, and despite their massive appearance – they aren’t as stable as they appear to be. There’s also no point climbing down any of the shafts or broken staircases. There’s nothing but darkness and concrete down there.
The Fernmeldebunker of the Lager Koralle is off limits, but can occasionally be legally visited. You can contact Team Delta – which has been exploring and documenting the area legally with permission from the State here.
Lager Koralle Address and Map
Ive left out the exact location of the Funkempfangsgebäude bunker entrance. As mentioned above, too many people have sought to gain illegal access to it, and it’s suffered enough vandalism over the past year.