Submarine bunker Lager Koralle, U-boat HQ

In the silence you don’t know, you must go on. I cower in the pitch darkness ten meters below, unable to move, frozen still. Deafening silence, broken only by a solitary drip. DRIP! Then silence again. I can hear my heart beating. Heart pounds again before the next inevitable drip, steady as the last. DRIP! I flash a torch at the wall beside me. It glistens black. Wet. The drop falls again. DRIP! The only sound but for the thumping of my heart. I can’t go on, I’ll go on. I’ve made it this far.

Subterranean treasures are rarely easy to find. Submarine even less so. Armed with sketchy directions, hope and a rough sea idea, I set off, leave the road and cut through the forest. Trees, trees and more trees, more trees again, and more, more again, then there it is. Boom! A shock when it finally appears. Looming in murky light. Surrounded by a rusty barbed wire fence. The dilapidated shack I was looking for.
A “Betreten Verboten” sign confirms it. Flies swarm to greet me as soon as I defy it. One lands on my neck. Bites. A dog barks, somewhere. Christ, I hope it isn’t on the site. It sounds further away. Too late to turn back now anyway. Come on man, get a hold of yourself, get a grip!
I pull myself together, spot the hatch I’m looking for. A bee hums, something else rustles in the grass. I lift up the lid. A swarm of flies buzz up in my face. AAAAGH!! A gunshot. BANG! Another bark, closer. More gunshots, louder.
The hole is eight metres straight down. No steps, ladder, nichts, not what I was expecting, but fuck it I have to go now. I jam my legs on one side, my back on the other, and jimmy down like a peanut. No idea how to get back. Jacket ruined. I pull the flashlight out and proceed. I’m in the bunker!
Soon, however, I discover it’s not the right bunker. It was smaller and had less rooms than expected. Not what I was looking for. It leads me straight back to the dilapidated shack. I get out and start again, back through the trees.
More abandoned buildings present themselves, each with stories to tell no doubt, but I was looking for something specific.
I cycle on. Then I meet two oul’ lads ambling along through the forest. Vladimir and Estragon.
“Excuse me, do you know where the old bunker is?”
The smaller, younger one replies.
“Ah yes, that’s where the Russians used to store their rockets. They had them aimed at Berlin. Very bad. But there’s nothing there to see now. The bunker’s destroyed. I’m 71, you know!”
I didn’t, but thank him profusely all the same.
I wander on, eventually find gates. The gates I was looking for! I hurry in. More buildings, more, more, more, but where’s the fucking bunker? I’d about given up, had enough, when finally, I lift the manhole and see the ladder down, down, down…
This is it! I take a last look at the sky and plunge in. I’m here! I’m finally fucking here! I scurry down, heart in mouth, wary of previous tenants still hanging around. It’s dark. Darker than Thatcher’s soul. I can’t see a thing. I’m 10 meters underground, in the very bunker that controlled Germany’s feted U-boat fleet during World War II. Central command for submarines marauding the seven seas. It was here those poor fuckers on Das Boot would have been ordered to go past Gibraltar! Wow, just wow.
They began building here in 1939, for what was originally supposed to be a naval intelligence school. When all the falling bombs made Berlin somewhat uncomfortable, some bright spark decided the German Naval High Command should move here, to this heavily forested area in the middle of nowhere, via Eberswalde, where it moved first after leaving Tiergarten in Berlin.
The Befehlshaber der U-Boote (BdU), which was the part concerned with Germany’s submarine war, moved to what was codenamed “Lager Koralle” (Coral Camp) on Jan. 30, 1943, and began controlling U-boat operations shortly afterward under direction of German Navy Commander-in-Chief Karl Dönitz, later to achieve fame as Hitler’s successor.
Koralle’s end came in April 1945, however, with an air raid doing its bit on the 17th, and the Russians taking over on the 21st. Dönitz had already ordered the BdU to “Objekt Forelle” in Plön, near Denmark, before going on to Flensburg-Mürwik, even closer to Denmark, eight days later.
When all was already lost, Dönitz succeeded Hitler according to the mad fella’s last will and testament, though there was little to do at that stage but surrender and hope for the best. Dönitz led the short-lived Flensberg Government before undergoing trial in Nuremberg.
On his release from prison he gained further fame for creating the snack that bears his name, the Döner Kebab. It remains popular to this day.
The Russians took over Koralle of course, blowing up the flak bunker and the other overground bunker. Perhaps in gratitude for the lovely kebabs he made, they spared Dönitz’ house and the underground bunker, where the navy headquarters had been based over four levels. It had a barracks, officers’ casino, loads of telecommunications equipment and other army-type stuff.
Maybe that’s why the Russians kept it. They used the site as a munitions depot, storing the missiles previously mentioned by Estragon, or Vladimir.
As I said, it was dark down there, 10 meters underfoot. I actually felt I was in a submarine, not just a subterrain. The silence was deafening, excruciating. Nothing but the drip. Drip! Drip! Then thump, thump, the thump of my heartbeat. The loudest silence there ever was.
There’s not much to see, not even graffiti. Wet crumbling rooms, corridors, pipes, tubes and cans of fuck knows what. Crazy cans, silver, big, sitting there with tubes coming out.
The Russians must have stripped the place of all its U-Boot paraphernalia. Those Russians are parasites of the military world and will strip any military stuff they reckon is better than their own. Any military stuff then.
When there’s nothing to hear, you listen. I thought I heard a voice, a girl’s voice, a laugh. I stopped, listened again, but there was only the incessant dripping and thumping. It occurred to me someone outside could come along and close the hatch, sealing me in there forever, leaving me to lick walls for sustenance and grow big bulbous eyes to cope with the dark. Trapped forever with the ghosts of tortured submarine men.
I could imagine the clang of the hatch slamming shut. It wasn’t fun anymore, I needed to get out. I flashed the light along the dark empty walls, retraced my steps through holes, long forgotten corridors, empty doorways. It was endless, I hoped to fuck I didn’t take a wrong turn. The hatch was unrecognizable – it was almost twilight outside – but I finally found the damn ladder and emerged. I was never so happy to see the sky. Even heroes of the deep were happy to see the surface.

What
Lager Koralle. Between 1943-45 Germany’s Naval High Command Headquarters, (Führungszentrum des Oberkommandos der Kriegsmarine, or OKM). Central command center for the German U-boat fleet during this time.

Where
Two-thirds of the way to Lanke from Bernau, in off the road to the right. The site is in a northwesterly direction from the village of Lobetal. Here’s a map showing where what's left of the destroyed (overground) flak bunker is. The rest is nearby.

How to get there
See above. I got the train to Bernau and cycled from there. Even armed with directions, it took me a long time to find, however. The area is still heavily forested. It’s not signposted and the tracks go off in all directions.

Getting in
Find the hatch, go down the ladder. You’re in.

When to go
Daytime, definitely daytime. A fall here is very bad news, and I seriously do not recommend taking any chances in the dark. Obviously, when you’re down there it’ll be dark anyway, but you’ll want some daylight at least so you might see where you have to get out. Do not cut it fine, like I did, and leave it till twilight.

Difficulty rating
8/10. Finding this is the main problem. If I were going again, I’d probably bring a tent and overnight in the woods. It’s also very dangerous. Apparently there are munitions still on the site, so you might get a leg blown off if you’re unlucky.

Who to bring
Bring someone, for safety’s sake. Mobile phones don’t work here, neither in the bunker nor above it.

What to bring
A torch. Do not forget a torch. Make sure it’s a good one. In fact, bring two. A compass would be useful in case you get lost. Bring a camera of course, some beer for the road, perhaps a bottle of water too. And some grub. Prepare to be out for a whole day at least.

Dangers
Like I mentioned already, unexploded bombs, hidden pitfalls, rusty ladders, loose bricks, low ceilings. I’m guessing the underground bunker itself is sound enough but you never know. A helmet is not going to save you if it does collapse. At least there’s no security, unless you count the ghosts of tortured submarine men...

Disclaimer: Karl Dönitz didn’t really create the Döner Kebab. On his release from prison he wrote a couple of books, autographed postcards and answered correspondence until he died on Christmas Eve, 1980.

A Teufelsberg Tale

Lew McDaniel of West Virginia, USA, was stationed at Field Station Berlin atop Teufelsberg between 1968-71.
The US military veteran is helping to organize a reunion of his colleagues and co-workers in Berlin to mark the 50th anniversary of the first permanent spying facilities (SIGINT) on the hill in September. They hope to place a commemorative plaque there commemorating the site's Cold War service.
Mr. McDaniel, who worked at Teufelsberg as a linguist, got in touch with me after I wrote about the ongoing shenanigans at the site last November.
(That's him on the right, pictured in 1967 during his time stationed at Monterey, California.)
In the course of our email correspondence, he told me of happier times at the spy station from its heyday, before it was abandoned and then fell into the hands of money-making opportunists and vandals.
His words are better than mine, so without further ado, here they are:
“I am sure you have seen all the various T-Berg links on the web. There are a lot of them, some accurate and some not. No submarine tunnel, a favorite while I was there, no aircraft radar, and no secret escape tunnels.
“The first site on T-Berg consisted of mounted vans in the early 1960s or thereabouts. I am not sure when the first dome was built, but I think around 1963. During my time there, there was a single dome with metal structures radiating from it. I worked in one of them – hot in summer with no windows we could open and so cold in winter we wore coats, sweaters, and gloves. Gloves made typing very difficult so I cut the tips of the fingers out of mine.
“The dome was two stories atop a concrete central pillar. The dome was made of some kind of rubberized canvas and kept inflated by air compressors from a WWII German submarine. At times the wind would overpower the compressors' capacity. When that happened, the windward dome side would partially collapse, causing a klaxon to sound. Upon hearing it, we all got outside and away from the structure as quickly as possible lest the dome fall and take everything in it down. The normal air pressure inside the dome was high enough that technicians who had to work occasionally in the top part actually had to decompress on the way out to avoid ‘the bends’.
“The view from the surface of the Berg (hill) itself was phenomenal on a clear day. At night, we often saw flares firing off along what was then the ‘Wall’ on the western border of West Berlin. Most of the time, it was caused by animals tripping the flare trigger. Near the site, we often saw wild boars along the perimeter fence.”
Mr. McDaniel added that he left the US Army after his three year tour in Berlin was over. He taught Russian at West Virginia University for a while, and eventually retired as its computing director in 2000.
Well, my appetite was whetted, so I asked him for more information, and if he had any photographs of his time at Teufelsberg.
“I took no pictures of the site during my time there nor any of Allied military activity,” he wrote. “We were cautioned to not be photographed if we could help it. However, Soviet mission cars were in the Grunewald area a great deal and photographed away when they wanted. They were pretty easy to spot – black low grade Mercedes with diplomatic plates and RDF antennae on the roof.
“Work there was a mix of excitement at times, coupled with normal business at others.
For most of my time there, I worked around the clock regardless of shift when there was urgent work to be done. I remember several three-week stints when I barely bothered to leave. Usually there was an even flow of things to learn and look out for that made the work very interesting – had my wife at the time not wished otherwise, I would have remained in the Army for a career.
“We were keenly aware the Soviets and the East Germans considered T-Berg a prime, first shot target and could have readily obliterated us. Berlin was after all within very easy striking distance of several Soviet tank, artillery, and rocket divisions. Teufelsberg would have literally been vaporized within less than a second after the command to fire was given and that command would have been one of the first.
“We were a military installation with concordant rules and regulations, but for the most part we were left alone to do our jobs. While we were certainly in the Army, wore the uniform, and followed the rules for the most part, we did not feel like we were part of the ‘regular’ army that toted rifles and slept in tents and such. I don’t mean to sound like a snob, but our talents were more suited to what we did than to being regular line troops.
“We were also dedicated partiers and nightlife people. We worked rotating five-day shifts and at end of the five days, many folks headed for the bars or to gatherings. Not many folks left Berlin – we could only travel via the American or British duty train or via American flagged aircraft and were not allowed in East Germany or East Berlin – so leaving the city was time consuming.
“We lived in an apartment in Steglitz, so I was not subjected to life at Andrews Barracks where most were quartered, other than the first week I was in Berlin. My original assignment after language school was to the US Military Liaison Mission in Potsdam. However, the Army realized shortly after that that I was married and changed the orders. Married personnel were not posted to Potsdam.
“Living on Maßmann Straße in Steglitz was interesting. I was issued two weeks of C-rations in case the balloon went up and given an airline ticket for my wife for the same situation. I always felt neither would be of any use – see the comments above regarding the forces around Berlin. When I departed Berlin, I had to turn in the rations and the ticket.
“The folks who lived in the other apartments there were nice. We were invited to their parties and family events and we often reciprocated. The Hauswirt and her husband were Czechs who came to Berlin before the Wall was built. We often took them cigarettes, bourbon, and beef and they cooked Czech meals for us now and then. We downed copious quantities of excellent Rumtopf they seemed to always be making.
“Before that, we lived on a street over off Clayallee in a house that belonged to an old couple who had lived there through WWII. They said their house was occupied at one time by Russian troops who were civil enough, but didn't seem accustomed to a regular house.
“What we did and how we did it remains cloaked in secrecy still. I can tell you the Army was in dire need of Russian linguists when I signed up in 1967. Which I did after receiving my draft (conscription) notice – draftees during the Viet Nam war did not usually have a choice of what they did in their two years in the Army, so I enlisted for four years in order to get a better opportunity to do something interesting. I originally wanted to be a helicopter pilot, but discovered during testing for that that I am color blind and that disqualified me... So I was asked if I wanted to be a linguist. I said sure, how about German, since I had four years of German courses in college. But they needed Russian linguists and sent me to the Defense Language Institute in Monterey, California for nine months. Last time our vets group held a reunion at the institute, Middle Eastern language courses were the largest group – not much Russian taught there now that the Cold War is over.
“Hope this was informative.”

Mr. McDaniel (left) now lives with his wife 26 miles south of Morgantown, West Virginia, in the middle of a forest.

All photos (except those of Mr. McDaniel) were very kindly provided by the US Army Intelligence & Security Command. Many thanks especially to Mike Bigelow for his assistance.

Teufelsberg (Abandoned spy station)

A Cold War relic lies abandoned on top of a mountain made of rubble, built over a Nazi college that couldn't be destroyed after the end of World War II. The gates of the former US spy station are locked and secure; its perimeter sealed by an uncompromising high fence, an angry crisscross mesh of wires that clearly imply: “Eintritt Verboten!”

Welcome to Teufelsberg, literally “Devil's Mountain,” a hill reaching 114.7 meters above sea-level, made from an estimated 12 million cubic meters of war rubble (apparently about 400,000 bombed houses) pushed together in the north of the Grunewald forest in West Berlin.

Buried deep beneath is what's left of a planned Nazi-military training school designed by chief Nazi architect Albert Speer. So sturdy was it that attempts by the Allies to destroy it failed, so they covered it with rubble instead. There was plenty of it around at the time. Every day, 80 truckloads of 7,000 cubic meters of rubble collected mostly by local women used to arrive. They became known as Trümmerfrauen or “rubble women” for their efforts.

Perched atop this (wo)man-made mound now sits the old abandoned listening or intelligence-gathering station used during the Cold War by the Americans and British to learn what was going on in Russian-controlled East Germany. It wasn't very discreet; three huge bulbous globes, two “radomes” perched atop buildings three-stories high and another sitting a further six-stories higher, creating a giant condom-shaped tower.

I mean, the Ruskis must have known this stuff was here, especially as it was built on Berlin's highest “mountain.” Maybe the Amis wanted to taunt their foes with their phallic handiwork. Evidently it was a source of great pride.

Due to its unique fucked-up history – a starring role in two World Wars and its subsequent division between the world's superpowers – Berlin found itself at the center of the so-called Cold War. This had nothing to do with nuclear snowballs, but was a pseudo war that flattered to deceive and ultimately never came to fruition despite the considerable expense accrued by its protagonists. Another considerable waste of money and illustration of human folly.

Spying and surveillance were the order of the day in divided Berlin. American mobile listening units, eavesdropping on Soviet and East German communications in the late 1950s, discovered they got better reception and coverage from the top of the 115 meter-high Teufelsberg. Quelle surprise!

The first mobile units took up position atop the hill in July 1961, with more permanent facilities following in 1963 before Field Station Berlin Teufelsberg gradually grew over the following years to become one of the West's largest spying stations ever.

As the mountain was in fact located in the British sector of Berlin, the Brits and Americans cooperated on their spying programs. (Presumably this means the Brits did whatever the U.S. National Security Agency told them to.)

USM 620 Kilo, as it was also known, was part of the worldwide Echelon spy network. Each radome globe contained massive 12-metre satellite dishes and the most sophisticated spying equipment for the time, enabling the western powers to intercept satellite signals, radio waves, microwave links and other transmissions, before interpreting and analyzing their findings. It’s clear that they didn't really trust the Ruskis that much. The feeling was mutual.

Contrary to common belief, however, there was no radar equipment ever installed at the facility.* There was no need for it. Radar is used to detect objects (such as airplanes, missiles, terrain) and the Allies already had radar facilities at Tegel, Templehof and Gatow airports. Teufelsberg’s function was to listen – nothing more.

Field Station Teufelsberg lost its raison d'être after the fall of the Berlin Wall and end of the Cold War, and was eventually abandoned in 1992 to the Wildschwein that allegedly call Grunewald home. The Americans used to call them “Grunie Pigs.” I didn't meet any of course, proving again beyond a shadow of a doubt that they don't exist.

In 1996, the 4.7-hectare site was sold to developers for 5.2 million Deutschmark, and they started with their plans to build “exclusive” apartments (must have taken their cue from Irish developers), a hotel and restaurant, as well as a spy-museum. Spiraling costs put paid to all that however, and the project was abandoned mid-construction after reaching debts of €50 million.

In February 2008, filmmaker David Lynch tried buy the place along with some crazy foundation of meditationists and yoga-bashers who wanted to build a “Happiness College” featuring a 12-storey 50-meter high “Tower of Invincibility” to house 1,000 students. The city turned down the proposals for some reason.

Another group of hopeless romantics, nostalgic for the good old Cold War days, want to preserve the remains of Field Station Teufelsberg as a memorial. They bemoan the damage caused to their beloved spy station by vandals and other unwanted visitors. The “Save Teufelsberg” campaign is now in full swing.

No new buildings can be erected on the site after it was declared part of the surrounding forested area in 2004, though the developers still retain hope of constructing apartments in the existing buildings. Negotiations are ongoing.

There was a time curiosity appeasers could enter through the broken fence and go in for a wander, but opportunists have taken advantage of the ongoing uncertainty by leasing the land and charging visitors admission. So ist Berlin. The group claims to be protecting the vandalized buildings from vandals. Sometimes they offer tours too. The fence has been repaired and thuggish security guards demand money from those who jump over it.

The situation is likely to continue until the developers and city agree on Teufelsberg’s ultimate fate. Of course, it would be great to see it restored/preserved, but that all costs money the city doesn’t have and developers don’t give away without something in return.

Meanwhile, I’ve had to update the visiting guide below to reflect the current situation. You can either take your chances with security or simply cough up the money they demand. Fittingly perhaps, it’s a devil’s choice.

What
Field Station Berlin Teufelsberg (Abandoned listening/spy station and Cold War relic.)

Where
Teufelsbergchaussee, 14193, Berlin.

How to get there
Get the S-Bahn, S9 or S75 to Heerstraße, or S1 to Grunewald and walk/cycle from there. Map can be accessed here.

Getting in
From the carpark simply walk the paved “Dragonfly street” path until you come to the fence. It’s much better fortified since someone noticed there was money to be made. If you follow it around you’ll come to the main gate. It’s the easiest entrance point but from there you’ll likely have to contend with security.

When to go
Daytime is better for observation purposes. Teufelsberg also provides good vistas of the city of Berlin. Nighttime could be good for parties, though care should be taken not to fall drunkenly from the unsecured tower. Fall soberly if you have to.

Difficulty rating
8/10 if you plan on avoiding security, 1/10 if you accede to paying them.
 
Who to bring
Friends for a party and exploration. Girlfriend/boyfriend for a romantic vista over Berlin.

What to bring
Camera. Beer. A torch. Maybe a few sandwiches. All that exploring can be hungry work!

Dangers
Not all ladders in the towers are secured to the concrete. Be careful! Luckily I was able to climb back down the one I ascended, or I'd still be there now.
Wind. It can get very breezy on Berlin's highest point. Most of the surviving buildings don't have walls so be careful you don't get blown off.

Again, spread the word, and suggestions for other abandoned and dangerous sites to be explored would be most welcome!

*I had this confirmed by Reinhard von Bronewski, whose excellent Berlin-Brigade site is a treasure trove for anyone interested in U.S. operations and sites during the Cold War in Berlin. Mr. von Bronewski said he'd spoken with many former Teufelsberg military police and troops, including high-ranking officers, and they all said the same thing: “This was no radar hill.”

This post has been updated from the one that first appeared on June 26, 2009, to take the latest developments into account, add some historical details, more photos, and make some other general improvements. All photos were taken on June 23, 2009.

Wolfswinkel and the monsters: The abandoned paper mill

Monsters now call the abandoned paper factory of Wolfswinkel home, transforming it into a magical fantasy land only the intrepid dare enter.
Well, you could just ask at one of the businesses out the front if you can go in for a peak but where's the fun in that?! Far better to sneak in as we did and have the wits scared out of you by the marvellous mystical creatures who have appropriated the crumbling buildings left over from a country that no longer exists.
I was thankful for the company on this occasion, accompanied as I was by fellow lovers of decay and ruin, andBerlin and the Digital Cosmonaut. Alone, I'm not sure I would have survived the experience.
After squeezing in at the back beside the river through a loose fence we tiptoed into their lair, though we weren't aware of their presence at the time. We stepped around the broken glass, careful not to make it crunch underfoot. Futile. Then we saw them through a broken window, the first monsters, eating a rainbow. As monsters do.
We proceeded, cautiously, perhaps foolishly. I peeked into a doorway that led into what most have once been a warehouse. There we encountered the next one, standing with arms outstretched and head back in deep existentialist contemplation. How he could think at all is beyond me, for just a few short metres away was a strange bird-like creature playing guitar, with an even stranger being firing what looked suspiciously like an old blunderbuss into the air. I was about to ask the strange-looking fella where he got it – they're few and far between these days – but thought better of it. I wasn't sure if he was shooting an accompanying beat to the music or warning shots to keep intruders away. Besides, the bird-like creature had a sharp-looking sword and more monsters were lurking nearby – one of them with an axe. I left them to their party.
We went on and found ourselves in a gathering on old redbrick buildings, their soft shades complemented beautifully by the encroaching moss and vegetation. If it's not the monsters...
The outer buildings are in a sorry state, smashed and shorn of roofs allowing the elements wreak their thing. But the main one is still fairly sound, broken window panes notwithstanding, and it's there that you get an appreciation of the factory's former glory and its raison d'être. It's also home to monsters. Loads of them.
The Wolfswinkel paper mill was the only in the area to produce handmade paper until the monsters took over in 1994. I'm not sure if they actually caused production to cease or some other terror brought about its demise. Their timing is certainly suspicious.
Whatever was responsible, it ended a production line going back to 1751, when the Spechthausen paper mill began operation in Eberswalde. Friedrich II of Prussia, a.k.a. Frederick the Great, gave Jean Dubois of France the official seal of approval in 1781, and before you knew it – well, in 1799 – it was also producing banknotes and securities as well as the aforementioned handmade paper.
From 1874 to 1945 it produced treasury notes and nearly all banknotes, letters of credit, cheques, stocks and other other securities for the German Reich.
Spechthausen provided the paper for Operation Bernhard, a dastardly plan hatched by the Nazis to destabilize the British economy during the war using forged banknotes made the master forger Adolf Burger in the nearby Sachsenhausen concentration camp. I don't think I've come across a plan more dastardly. Burger's still on the go, 95 years young, and living in Prague. They made a fine film out of the whole thing called The Counterfeiters, Die Fälscher in German. And you thought this post was only about monsters.
Spechthausen, like pretty much everything, was gradually wound up after the war. The production of the handmade paper was transferred in 1956 to the Wolfswinkel plant, which had been in operation since 1765. Wolfswinkel began production of the Spechthausen brand from August 1 the following year. The age-old traditional methods were retained and each sheet of paper still featured the famous “Spechthausen 1781” watermark comprising a woodpecker (Specht) and a tree.
I looked up the processes involved but they're probably not worth getting into without risking boredom. We certainly don't want that here. If you're into the processes, you'll be able to find out plenty somewhere else on the oul' interweb I'm sure.
Of course, the Russians took over the original Spechthausen plant. It's telling that the monsters waited until they were well gone before they even thought of moving in.

What
Papierfabrik Wolfswinkel-Spechthausen. Abandoned paper mill that once produced the famous Spechthausen handmade paper, a brand which went back to 1781 when Frederick the Great gave it his seal of approval. Since taken over by monsters.

Where
Wolfswinkel, 16227 Eberswalde. It's on Eberswalder Straße, roughly number 33-34-35. Not sure which, but once you get there you can't go wrong.

How to get there
Get the RE3 regional train in the direction of Stralsund to Eberswalde. It goes from both Berlin Hauptbahnhof and Gesundbrunnen, takes half an hour from the former, less from the latter. You can get the 861 bus from Eberswalde station to Finow, Wolfswinkel. Once you get there walk along the road until you see the gate with scarily accurate “End of Summer” sign. That's what you're looking for right there. You can also just cycle along in a westerly direction from the train station until you find it..

Getting in
As I mentioned earlier, you could just ask in front if you can go in for a gander. I don't they'll mind as long as you don't look like you're going to thrash the place. There are people living there (despite the monsters) and I'm sure they don't want hordes of people poking around their stuff. Otherwise you can just sneak in around the side – watch out for yer man snoozing in his van – and snoop around without getting caught. More exciting in my opinion.

When to go
Don't go when it's raining (as we did) or you'll get soaked, especially if you cycle (as I did). Best to go during the day. I don't think this is a party venue, unless you ask the folks out front and they're more obliging than I thought.

Difficulty rating
5/10. Quite easy, both getting to it and in.

Who to bring
Someone who's not afraid of monsters.

What to bring
Bring a torch, a camera and a couple of beers. Something to eat would be good too. I didn't, and was flippin' ravenous by the time I got back to the train station. I'm getting hungry again just thinking of it now.

Dangers
Nothing major to worry about. You always need to take a certain amount of care in these places in case a roof lands on your head but this was one of the more structurally sound structures I've been in. Of course, there's always the little matter of the monsters.