Citymapper led us along this unmarked trail and into the forest in the distance.
After walking through the trees, we eventually got a glimpse of the "radomes," which were built in the 60s. A radome is a structural, weatherproof enclosure that protects a microwave antenna, like a radar.
We found the entrance and paid €7 to get in. This car was found at the bottom of one of the spy towers.
We were treated to a stunning view across Berlin and the Grunewald Forest after ascending several sets of stairs.
The radomes were once home to rotating satellite dishes, some of which measured around 12 metres. Locals referred to the radomes as "Berlin's Balls."
The fabric that covers the dome structures has been ripped and torn, either by the elements or by vandals/artists.
Teufelsberg aimed to expose the Communist Bloc's secrets to analysts and linguists working for US intelligence agencies and Britain's Government Communications Headquarters (GCHQ).
The analysts noticed that during certain times the reception of the radio signals was better than during the rest of the year. The "culprit" was found to be the Ferris wheel of the annual German-American Volksfest Festival.
The US chose to run spying operations from Teufelsberg after realising that the 120 metre hill was the perfect vantage point to intercept Soviet communications.
Access to Teufelsberg was restricted after the site's closure when the Berlin wall came down.
A group of investors bought the former listening station area from the City of Berlin in 1990 with the plan to build hotels and apartments, while preserving the listening station itself as a spy museum. However, the project was aborted after the developers realised it was unprofitable.
The site is now an artists' playground and comune. Visits to view the graffiti art and gain access to the domes are still possible, although be careful as there is broken glass in places and other hazardous objects. Striking murals like this one can be found within the former NSA buildings.
Several of them — including this one — make geopolitical references.
The Soviets beat the US in the Space Race — a 20th-century competition between the Cold War rivals for supremacy in spaceflight capability.
A tiger mural can be found in the highest dome.
Lower down in the complex, a shark approaches a zebra fish with its mouth wide open.
This dog popped up in several places, each time with a different speech bubble.
The site is home to other works of art beyond murals. These bikes, for example, have been built into a wall.
While this face sits on a stand inside the main spy building.
Not all of the buildings are easily accessible.
In 2006, the Teufelsberg was categorised as forest in the land use plan of Berlin, thereby eliminating the possibility of developers moving in.
Several novels have been written about the Berlin field station including "Death On Devil's Mountain" by David Von Norden and "McCurry's War" by Chuck Thompson.
There are fun things scattered around the site for people of all ages to enjoy.
If you'd still like to learn more about Teufelsberg then you can watch this YouTube video.
