Berlin's denouement at the end of World War II is best viewed below street level by touring the maze of tunnels built out by the Nazi regime. While popular with tourists, these subterranean journeys only touch on the fringes of this honeycomb of evil -- the infamous bunkers of Adolf Hitler and his lieutenants were either destroyed or walled off.
Often, the journey down into Germany's troubled past begins unexpectedly.
In an inconspicuous house in Badstrasse in northern Berlin, for example, a door opens suddenly on to the entrance of a former air raid shelter at what was once a metro subway station. The steel door leads down into an underground web of poorly lit corridors, with thick concrete walls and heavy steel doors.
Some of the rooms have a unique feature – they remain illuminated after the lights are turned off.
“The walls were painted with a special phosphorescent substance to help people find their way in the air shelter in case of an electricity blackout,” said the guide from Berliner Unterwelten, or Berlin Underworlds, a non-profit organization that offers tours of several bunkers in the city.
The bunker complex is also equipped with subterranean bathrooms, kitchens and even underground postal tubes, designed to move mail at a brisk 100 yards per minute – the forerunner of the fax, so to speak.
The Soviets tried to level the landmarks of Nazi Germany, including Hitler’s, which they partially destroyed, to prevent the sites from developing into neo-Nazi shrines.
Although underground, the rooms were built not as air-raid shelters but as work and storage rooms for the underground railways. They lacked sufficient reinforcement to withstand a direct bomb hit. But Berliners who took shelter there during the hundreds of bombing raids in World War II never knew that – they just wanted any form of protection, no matter how insufficient.
The tour of the air-raid shelter at the underground metro station is one of several offered by Berlin Underworlds. They include the ruins of a flak tower in the city’s Humboldthain park and a gasometer bunker on Fichtestrasse.
“From 1935 onwards, many bunkers were built,” said Bjoern Weigel, a historian at Kultur Projekte Berlin, a not-for-profit cultural group.
“As the war started and Berlin got bombed, even more were constructed, also at ground level,” Mr Weigel said. He is helping to organize exhibitions and tours on the 70-year commemoration of World War II’s end in April.
Numerous bunkers in Berlin were bombed during the war. Between 1945 and 1949, the Soviets tried to level the landmarks of Nazi Germany, including Hitler’s, which they partially destroyed, to prevent the sites from developing into neo-Nazi shrines. Hitler’s bunker was just part of a network of bunkers, some of them connected, in the government quarter south of the Brandenburg Gate.
In the late 1990s, city authorities discovered the bunker that ran underneath the villa built for Josef Goebbels, Hitler's propaganda minister. It is close to the Memorial to the Murdered Jews of Europe, as is Hitler’s bunker.
Not far away is the bunker for the drivers of the “Schutzstaffel” or SS, the most powerful military unit in the Third Reich. It was also discovered in the late 1990s.
Neither of these bunkers is open to the public and may never be, for political reasons as Germans attempt to discourage the sites from becoming shrines for neo-Nazis.
In southern Berlin, Tempelhof airport, which was built between 1936 and 1941 and is now a city park and open field, has its own underground world. Beneath the wing-shaped terminal, one of Europe's largest buildings and a prime example of Nazi-era architecture, are the remains of a Messerschmidt airplane factory.
The basement levels also contain the "Film Bunker," a series of rooms with reinforced walls and ceilings used during the war to store secret films and photo negatives.
“I can now imagine better how it must have been for people to live in these conditions,” said 44-year old Britta Brostowski, after a recent tour of an air shelter.
But Berlin’s subterranean topography was home not only to millions of people seeking shelter during the war, but also billions of beer kegs over the decades. At the beginning of the 20th century, the city had more than 200 breweries, all of which needed cellars for cooling and aging their products.
Because the water table in the city is particularly high, breweries were historically built on higher ground, in areas like Prenzlauer Berg and Kreuzberg-Neukölln, to allow sufficient space for deep underground cellars. Many were used as makeshift civilian bunkers during the Second World War too.
The former Bötzow brewery and its beer garden, located in the district Prenzlauer Berg north of Berlin’s city center, are home to 150-year old underground storage rooms, totaling 5,000 square meters, almost the size of a football field. In the south part of Berlin, people can visit the cellars beneath another brewery, at a former Kindl storage cellar, located in the district of Neukölln.
Another brewery is open to view – and comes with an escape tunnel. The former Oswald Berliner brewery’s underground storage was cleared from rubble, and opened to the public in 2011. In the cellar, Berlin Underworlds has built a replica of Berlin Wall escape tunnel at original size, 12 meters long. When the Wall split the city in East and West before it fell in 1989, people dug tunnels to escape from communist-ruled Berlin to West Berlin, which was part of West Germany.
Interest in happenings below ground is rising. Visitor numbers to Berlin Underworlds’ museum and its underground tours have increased from 3,000 in 2001 to 300,000 people in 2014. The organization, which doesn’t receive state funding, uses the proceeds from the visits to pay for its staff and to maintain the underground sites, which are mostly owned by city authorities.
Without the association’s activities, some sites could actually fall into ruin, according to Holger Happel, spokesman for Berlin Underworlds. “If an underground site is not used, it would deteriorate due to damp, for instance,” he said.
The tours, he added, also help to finance the development of new sites and save them from being forgotten. Berlin Undergrounds took over a 164-year old water management plant last year to keep it open to the public.
And for those willing to drive 45 kilometers, or 29 miles, north of Berlin, a project is underway to open up to the public the atomic bunker of the former East German leader, Erich Honecker. The three-story complex, completed in 1983, and the surrounding area are not yet accessible but a team of volunteers is working to turn it into a museum.
Who would have ever thought that Berlin’s bunkers would someday be tourist magnets? Certainly not their builders.