Berlin's past is everywhere, and its people never forget, writes Ben Groundwater.
There's still a spy in the old US listening station. Christopher McLarren looks every bit the spook today with his cloth flat cap, long beige trenchcoat and black leather gloves. He paces the area outside the gutted, graffiti-covered spy base in West Berlin, telling stories from the not-so-distant past.
"We had to know the Soviets as well as we knew ourselves," he recalls. "We had to know their codes and their call signs. We had to know the people we were listening to."
McLarren spent three years here at Teufelsberg working as a radio analyst at the height of the Cold War. On a hill near a forest on the outskirts of Berlin, this was a joint US and British field station, a place where radio conversations from around the Eastern Bloc were scanned, recorded and carefully studied.
It was said you could hear all the way to Moscow from these big white domes whose now-tattered coverings flap in the cold breeze.
McLarren has been running tours of his old workplace for a few years now - although 2014 is bound to be his busiest.
There will be an increased interest in Teufelsberg this year, and in all of Berlin's Cold War-era relics, because on November 9, Berliners of the east and west will celebrate the 25th anniversary of the fall of the Berlin Wall.
Twenty-five years since a botched press conference emboldened first a few, and then thousands, and then an unstoppable wave of East Berliners to cross and then destroy the hated wall. Twenty-five years since a peaceful revolution reunited Germany. If ever there was a good time to explore the old Berlin, it is this year.
Teufelsberg certainly retains its place in Berlin's Cold War story, although it doesn't look quite as impressive today as it must have during its heyday at the centre of the West's radio operations.
Once scheduled to be destroyed to make way for an apartment development, Teufelsberg was stripped and gutted, but when those building plans were scrapped, the field station was left to decay.
It lives on. There's always been an interest in history in Berlin, and the citizens of the western side of the city, in particular, are loath to let a site such as Teufelsberg completely disappear. That's why the radio domes, huge spheres covered in white cloth, have been restored to complete the city's skyline.
The stories McLarren tells today as he leads us through the complex are straight out of a spy novel - tales of agents and double-agents, of clandestine meetings, dead-drops and midnight runners.
We take a full tour of the facility, from the old armoury to the rooms where McLarren and his colleagues would analyse the radio intercepts, to the inside of those huge white domes, now covered in graffiti.
Teufelsberg retains an important place in the German capital's psyche.
More than 60 per cent of the people who take the tour here, McLarren says, are Berliners. "They love to explore their own city."
Given the state of disrepair the old listening station is in, the only way to see Teufelsberg is by taking this tour, which is not only a great way to explore the facility, but a chance to listen to tales of the Cold War from one of its participants.
"Life was good for US soldiers in West Berlin," McLarren recalls. "We had the run of the city. We could cross into East Berlin and exchange money on the black market and go on huge shopping sprees - fine china, Zeiss camera lenses ... we could afford it all over there."
Modern-day Berlin is just as ripe for exploration. It's a network of historic buildings - the famous ones, such as the Reichstag and those on Museum Island - and then the not-so-famous ones, buildings from Cold War times that have been abandoned, but not forgotten.
One of the most incredible of those is Tempelhof. Once one of the largest buildings in the world, this Nazi-era airport terminal now sits empty in central Berlin in a huge open field, a patch of grass criss-crossed by deep gashes of tarmac.
Tempelhof was built as a show of strength by the Nazis in the 1920s and '30s, and during the Cold War was the lifeline to West Berlin. All food rations or supplies brought in by the West had to pass through here.
The famous "candy bombers" took off from here. For West Berliners, this airport was a symbol of freedom and hope.
After the fall of the wall, Tempelhof became Berlin's commercial hub, only to be abandoned in 2008 due to its short runways and inner-city location.
Now, the huge terminal stands cold in the wind, an imposing block of Nazi-era stone begging to be explored. And that can be done, with the recent introduction of English-language tours. Today I'm exploring with Stefan, an employee at Tempelhof with a serious passion for this impressive building.
It's eerie as we step inside the hollow old terminal, like being on the set of a zombie movie.
Our footsteps echo off the stone walls as we walk through the old departure lounges, heading for the main check-in area, a huge hall with sky-high ceilings and marble floors.
"Do you know," Stefan says, gazing at the hall from a balcony above, "that there's a military planning room right below the check-in area? Right at people's feet, there were Nazis and then Americans planning for war. Just below their feet!"
On the very top level of the terminal there's a gym and bowling alley once used by American soldiers. Down the stairs, past ground level and deeper, lie the military facilities, the planning rooms and living quarters.
Even more interesting are the bunkers and air-raid shelters deep below the airport grounds.
Stefan walks me down to this area and there's a strange, perceptible shift in energy as we enter the dark rooms where the Nazis would once hide. It's spooky down here - far spookier than the empty departure halls. We'll go even further underground, too, to old storerooms whose thick concrete walls are still marked black by old fires.
It's a relief to get back up to ground level and take in Tempelhof from the outside - huge, imposing and silent.
Later, Sebastian, our guide for the day, asks: "Do you know why the East Germans built the Berlin Wall?" One of the clients raises his hand. "To keep the capitalists out?" Sebastian smiles. "That's right - to keep the capitalists out."
He sweeps his hand past a long expanse of graffiti-covered concrete wall. "And this is where they did it."
We're standing in the Mauer Park, just near where the first breach of the wall famously took place.
This long, narrow patch of grassland in northern Berlin is similar in size and shape to many dotted across the city - a legacy, Sebastian explains, of the wall.
"Any parks you see like this," he says," was probably once part of the Death Strip, the no-man's-land between the two sections of the Berlin Wall. The city decided to keep it all as open space."
Part of the wall has been left standing in the Mauer Park, and it makes an excellent introduction for our Berlin on Bike tour, a three-hour cycling trip tracing the path and history of the old wall.
We began just nearby in Prenzlauer Berg, a suburb that was part of the old East Berlin, and where small remnants of the wall can still be found. "The wall will always be there," Sebastian says.
"Look on the pavement, you'll see a metal line that shows you where it once was. Look along its old route and you'll find memorials and murals. The people of Berlin will never forget it."
In Prenzlauer Berg, which is now a beautiful suburb full of restaurants, cafes and perfectly restored apartment blocks, some of the first attempts were made to cross the wall. East Berliners would leap from buildings that backed onto the Death Strip - eventually those buildings were destroyed, leaving what is now a bright, open space down by Bernauer Strasse.
It's an incongruous sight today to see families playing in the grass of the old Death Strip, flanked on each side by huge murals on buildings, historic photos of East Germans attempting to cross the wall.
That's the new Berlin for you - free and happy, but shadowed by the past.
We jump back on the bikes and head down to another park on Bernauer Strasse, another part of the Death Strip that has been turned into a memorial.
This is the only segment of the wall with a preserved section of no-man's-land in the middle; cracks in the concrete wall allow visitors to peer through and get a feel for the task that faced those with the will to escape the east.
"This area wasn't a nice place to live," Sebastian explains. "The politically correct East Germans, the ones the government liked, were put in houses on the outskirts of the city. The people with more 'alternative' views had to live near the wall. It created a spirit of rebellion, a spirit of protest, that lives on in Berlin."
For evidence of that spirit, take a look today at almost any wall or building in the city. It will be covered in street art or graffiti, which may seem like mindless vandalism at first sight, but has a history dating to Cold War times.
On an Alternative Berlin walking tour through some of the grittier, trendier parts of the city such as Kreuzberg and Neukolln, our guide, Mark, explains that early West Berliners with a few cans of paint and something to say had the perfect canvas to voice their concerns.
What began with a few scrawls of protest on the west side of the wall morphed into a riot of colour over the Cold War years, a mix of artistic expression and political activism splashed across the most visible symbol of the communist east.
That tradition never disappeared, and today Berlin's apartment buildings and warehouses are still awash with murals, slogans and tags. Even Teufelsberg, the old listening station, hasn't been spared, its gutted walls covered in the works of local artists forever linked to the past.
The Cold War is over. The wall has come down. But Berlin will never forget.
The writer travelled as a guest of Emirates and Visit Berlin.
FIVE MORE BERLIN ATTRACTIONS
MAUERPARK FLEA MARKET
This Sunday market contains a treasure trove of antiques and bric-a-brac, and is always packed with locals and tourists.
The largest palace in Berlin is also the most impressive, with its baroque and rococo architecture, formal gardens, theatre and pavilion.
KAISER WILHELM CHURCH
If ever a church could sum up a city, it's this one, a mixture of old and new, a church spire partly destroyed in World War II, and a modern belfry and foyer that act as the church's current place of worship.
One experience that appears on most to-do lists for visitors to Berlin is climbing the dome of the Reichstag building, where German parliament meets.
A visit to this fortress not only means you get to check out a well-preserved Renaissance-era military structure, but you also get to explore Spandau, a suburb that feels a world away from the bustle of central Berlin.
Emirates flies from Sydney to Frankfurt, Dusseldorf and Munich, with connections to Berlin. Economy return starts at $2039. Phone 1300 307 777; see emirates.com.
The boutique Monbijou Hotel has rooms in the suburb of Mitte, walking distance from Museum Island and most of inner Berlin's major attractions. Rooms start from $96 a night. See monbijouhotel.com.
Christopher McLarren's tours of the Teufelsberg listening station go for about 90 minutes, and cost $22. See visitberlin.de.
Tours of the Tempelhof Airport terminal cost $19. See tempelhoferfreiheit.de.
Berlin on a Bike's guided Berlin Wall tours cost $27, and go for about three hours. See berlinonbike.de.
For free Alternative Berlin walking tours, including its subcultures, see alternativeberlin.com.