Berlin trucked the rubble of its bombed-out streets onto an unfinished Nazi military college for 22 years because the Allies had failed to blow it up, and the hill grew high enough that the NSA built a listening station on top, which sat abandoned by 1992 and is now covered in graffiti

Rising out of the Grunewald forest on the western edge of Berlin is a 120-meter hill crowned with torn white domes, like golf balls left behind by giants. The hill is called Teufelsberg, Devil’s Mountain, and it appears on no geological map of the region for a simple reason: it is not geology. It is Berlin, the old one, piled up and buried, with three separate empires’ worth of history stacked inside it like sediment.

Layer one: the college that would not die

At the bottom of the hill sits a building. In 1937, Albert Speer’s plans for rebuilding Berlin as Germania, the monumental capital of the Thousand-Year Reich, included a Wehrtechnische Fakultät, a military-technical college, on the city’s western edge, and construction began on a ferocious scale. The war it was meant to serve interrupted it; the shell stood unfinished through the bombing, and after 1945 the Allies decided to erase it along with the rest of the Reich’s military architecture.

They couldn’t. The structure was built so massively, with reinforced concrete engineered to monumental standards, that demolition charges made no useful impression, and blowing it up properly would have cost more explosive than anyone cared to spend on a ruin. So West Berlin’s planners inverted the problem. If the building could not be removed from the landscape, the landscape would be removed from the building: the indestructible college would be buried.

Layer two: the city itself

They had, conveniently, a city’s worth of material. Allied bombing and the final battle had converted much of Berlin into loose masonry, and clearing it, brick by brick, largely by the famous Trümmerfrauen, the rubble women, was the defining labor of the postwar years. Every district needed somewhere to put the debris, and the doomed college in the Grunewald became West Berlin’s official destination. From 1950, trucks ran in convoys to the site, and they kept running for 22 years, tipping the pulverized apartments, churches and factories of the prewar city onto the concrete shell until the pile held on the order of 26 million cubic meters of rubble, the remains of hundreds of thousands of buildings, roughly a third of everything the war had knocked down in Berlin.

By the time dumping ended in 1972, the pile had been landscaped, planted with trees, and equipped with a ski jump and sledding runs, and it stood as the highest point in West Berlin, a mountain made of the city it overlooked. Underneath the picnickers, entombed and intact, the Nazi college still stands, holding the whole thing up.

Layer three: the ears

The Americans noticed something about the new mountain before the grass had fully taken. West Berlin sat 160 kilometers inside the Eastern Bloc, a listening post fate had positioned in the enemy’s living room, and height is everything in radio interception. Mobile U.S. units testing sites around the city in the late 1950s found reception on the rubble summit superb, and in the early 1960s the U.S. Army Security Agency, working with the NSA and Britain’s signals services, built a permanent installation on top: Field Station Berlin, its antennas sheathed in the white geodesic radomes that give the hill its silhouette.

For three decades, the station listened around the clock, eavesdropping on Soviet and East German military radio, telemetry and communications from deep behind the Iron Curtain, one of the most valuable intercept sites of the entire Cold War and, reportedly, a contributor to the ECHELON network. A few kilometers east, the Soviets and East Germans listened back from their own towers. The mountain built from the ruins of one war spent the next one wiretapping, its foundations a Nazi ruin, its summit an American ear, its mass the pulverized homes of Berliners in between.

Then the enemy dissolved. With the Wall down and the Soviet Union following it, the station lost its purpose; operations wound down and by 1992 the Americans had stripped their equipment and gone, leaving the radomes empty on the summit.

Layer four: the paint

What followed was three decades of very Berlin limbo. The city sold the site in the 1990s to investors whose plans, hotels, apartments, a spy museum, all collapsed; David Lynch turned up at one point proposing a meditation university; vandals and weather shredded the radome skins; and the fenced, rotting station became a magnet for urban explorers. Eventually the caretakers stopped fighting the inevitable and licensed it: today Teufelsberg operates as a gallery and event site billed as one of the largest street-art spaces in Europe, its towers and halls layered in graffiti, its main radome famous for an echo that turns a hand-clap into a thunderstorm, with tours climbing past murals to the platform where the antennas stood.

Which completes a stratigraphy no one designed. A hill in a Berlin forest currently consists of, from bottom to top: the unfinished war college of a regime that lasted twelve years; the crushed remains of the city that regime destroyed; the abandoned surveillance station of the alliance that won; and several hundred layers of spray paint applied by the generation that inherited the lot. The Allies failed to demolish exactly one building in Berlin, and Berlin, with characteristic economy, used the failure as a foundation, the debris as a monument, the summit as a weapon, and the ruin of the weapon as a canvas. The devil’s mountain is the twentieth century, stacked in order, open for tours.