The first time I stepped inside this bunker, I was fascinated.
I had seen mineral formations in abandoned bunkers before, but never anything remotely like this. What we found inside was completely unexpected.
It was early March 2021 when a friend told me about a bunker not far from home. The entrance was open, although the structure would normally only have been accessible through an opening in the roof.
That was enough to make us curious.
We set off almost immediately, and just 20 minutes later we were already looking for a place to leave the car. Despite the rural surroundings, finding a discreet parking spot turned out to be surprisingly difficult. Eventually, we managed to find somewhere suitable and set off on foot.
Rubber boots were highly recommended - and we soon understood why.
In fact, there were two bunkers of identical design. They had been constructed during the Second World War as air-raid shelters for a labor camp, which housed workers employed at a large oil storage facility nearby. The facility had been developed from the late 1930s onwards as part of the area's wartime infrastructure.
According to the information we had received, the entrance was open.
So we stepped inside.
The history of the site had left its mark.
After the war, the camp was used as a reception centre for displaced persons. The bunkers themselves were later deliberately rendered ineffective as shelters by the British occupation forces. Their roofs and walls were perforated with pneumatic tools, destroying their original protective function.
Those openings changed the bunkers in another, completely unintended way.
For decades, rainwater, soil, leaves and other organic material had been making their way inside. The corridors were now filled with muddy earth and decomposing vegetation, while plants had taken advantage of the holes in the ceiling to grow inside the concrete structure.
But then we entered the rooms alongside the corridors.
And suddenly, the bunker looked completely different.
The floors were covered by between 10 and 20 centimetres of water. Along the damaged concrete walls, beautiful mineral formations had developed — and they covered much more of the bunker than I had expected.
There were stalactites hanging from ceilings and walls, while stalagmites had formed on the floors. Some of the formations had joined together, creating intricate structures that looked almost like the interior of a natural cave.
Except they weren't.
These formations had not taken centuries or thousands of years to develop. They had appeared within just a few decades.
A cave made of concrete.
The reason can be found in the concrete itself.
Due to material shortages during the Second World War, concrete containing a relatively high proportion of lime was used in the construction of many structures. Over the decades, water slowly penetrated the porous concrete. As it passed through the material, it dissolved minerals and carried them towards the interior of the bunker.
Once the mineral-rich water reached the walls and ceilings, it began to evaporate, leaving behind tiny deposits of calcite. Drop by drop, year after year, these deposits accumulated — eventually producing the remarkable formations we found inside.
The result was a strange combination of military architecture and a geological process normally associated with natural caves.
Outside, the bunker was slowly being reclaimed by vegetation.
Inside, the concrete itself had begun to grow its own cave.
There was, however, one less pleasant aspect to the experience.
The decomposing organic material in the corridors produced a strong smell of decay, despite the relatively cold water covering the floors. It was certainly not the most pleasant environment to explore.
But that wasn't going to stop us.
We made our way through every room we could access and spent a considerable amount of time photographing the formations, the flooded interiors and the traces of the bunker's past.
By the time we were heading home, one thing was already clear to me:
I would have to come back.
To find out more about the history and to check out all the photos from this place, click the button below.
