Teufelsberg Field Station on the fringes of Berlin was used by the British and Americans during the Cold War to spy on the Soviet Union. It's now a tourist attraction covered in street art.
Warning: Some of the street art in these pictures contains language readers may find offensive.
The station was abandoned by the NSA in the early nineties, and it took all its equipment and information with it.
Classified reports are due to be released about what happened at the station in 2022.
All we know at the moment is that around 1,500 spies worked here 24 hours a day over three shifts.
Now Teufelsberg has been reclaimed by graffiti and street artists.
The current landlord wants Teufelsberg to be a "natural cultural space."
A regeneration project announced earlier this year will see electricity, running water, heating and windows put in.
It will build on the artist's visits that already take place.
Painting on the inside of Teufelsberg's highest dome.
A piece of exercise equipment inside the station.
Visitors must sign a disclaimer when they visit Teufelsberg as the site is rife with hazards.
This tower was the first to be built and was analogue (the rest are digital).
Art by Victoriano from Brazil.
Nearly all of the site is accessible to visitors.
Sculpture is also present alongside street art.
The Teflon used to make the domes is delicate and has been damaged by vandalism.
Teufelsberg is surrounded by the Grunewald Forest. In the distance is Lake Wannsee.
Berlin's Olympic stadium is visible from the uppermost window of the tallest tower.
Visitors pay 8 euros to gain entrance to Teufelsberg.
There is a small bar and gardens for people to chill out in.
Many of the artworks contain a political message.
Each artist contributes to the project in their own unique way.
The domes were designed to let information in, but not out, as well as to disguise the equipment underneath.
Teufelsberg, which means "devil's mountain," is actually the name of the man-made hill on which the Field Station sits. However, it's surrounded by forest, making it hard to spot from a distance.
Views stretch far and wide across the surrounding countryside.
The NSA left behind very minimal equipment.
Visitors must pay an extra 7 euros to take photos on the site.
Getting there involves a 30-minute walk from one of the nearby S-bahn stations.
Outside is a makeshift bar, with relaxation areas and a ping pong table.
Each triangle used to construct the domes is a different size. Fitting them together is a complex mathematical problem.
Most of the high-up vantage points now have railings installed.
Artwork by Nick Flatt.
The current landlord wants the station to be a place of relaxation.
There are four domes in total at Teufelsberg.
Nyika Mukada is an artist and tour guide working at the listening station.
Sometimes jam sessions are held in the uppermost dome.
Wherever you go, you will stumble upon surprising artworks.
Parts of the site are very overgrown.
It's worth going to Teufelsberg for the incredible views of Berlin.