An urban explorer making his way through a vast 11,000-acre town built at the height of the Cold War says he was completely gobsmacked at the sheer size of the place. Colin Hodson, who chronicles his explorations on his Bearded Explorer YouTube channel, explained that while he had visited the town of Rheindahlen before, he hadn’t grasped how absolutely immense it was.

“People were saying to me after the last video we did of one of the housing estates, ‘You’ve missed so much’.” The vast development in Mönchengladbach, North Rhine-Westphalia, was once home to some 12,000 British service personnel and their families, but it has stood empty since 2013.

“I never realised that the whole place I was looking at was completely abandoned,” Colin said. “It’s just so big. I just think it was possible.”

Rheindalen served as the main headquarters for British forces in Germany and for the NATO Northern Army Group throughout the Cold War, springing up almost overnight in 1954 and remaining in use until 2013.

One of the most remarkable things Colin discovered on his second visit to the down was a fortified underground bunker that housed a vast map of the entire site. “We’ve got a map room,” Colin said. “This is incredible – there’s a whole map of the town there. We have just found a secret map room in this abandoned town… Oh my goodness me.”

Using a photograph of the site map as his guide, Colin was able to find the town’s shopping area, its church, and the cinema that was the target of an unsuccessful Provisional IRA bomb attack in 1973.

Colin said: “The town offered a wide range of facilities for both military personnel and civilians. These included accommodation, sports facilities, gym and sports grounds, a large swimming pool, recreational areas including cinema, youth club and NAAFI.

“At its peak. Rheindahlen was home to 12,000 British military personnel and their families. It housed the headquarters of the British Army, Royal Navy, and Royal Air Force. It was a significant base for the British forces throughout the Cold War and beyond.”

Colin was particularly impressed by the town’s massive open-air swimming pool, which isn’t completely drained, although the water has a little too much algae in it to invite swimmers today.

Despite plans to convert the site into a leisure park being put forward in 2015, and a later proposal to use part of it to house asylum-seekers, the massive town remains deserted. “Today, it is completely abandoned. Nobody goes there, only wildlife, and nature is slowly reclaiming the site,” Colin says.

Finding an unlocked door at the back of Rheindahlen’s Globe Cinema, Colin finds that the auditorium seating has been removed, although posters for movie such as Bruce Willis action flick 16 Blocks and Jenifer Aniston’s romcom The Break-Up litter the floor. Both films released in 2006, giving a sense of when the cinema was last used.

All of the posters are for English-speaking version of the films, and the safety notices in the cinema’s projection room are in English too, underlining the native language of the people who lived in this huge development in the middle of Germany.

In the town’s massively-overgrown police station Colin found a huge holding cell, seemingly intended to detain dozens of prisoners. The only occupant now, though, was one solitary dead mouse.