FOR MORE THAN 70 YEARS, phosphate mines were exploited close to the Wallonian city of Mons in Belgium. The phosphate, among other uses, was employed in the sugar industry and to make fertiliser.
To the local population the mines provided vital jobs and income, but in return they worked 13-hour days underground to delve the phosphate, spending year after year in harsh conditions and always in physical danger.
Child labour was normal in those days, and the youngest miners were barely 12.
The phosphate deposits were discovered in 1875 and the mining continued until the 1950s. Hundreds of thousands of tonnes of this precious commodity were brought to the surface during this time.
In World War Two the mines were also used by the Resistance to hide away refugees and weapons.
When the phosphate-mining stopped and the mines were closed, they found a later purpose as a mushroom farm. Meanwhile, a large part of the mines had been flooded by rising groundwater.
This water was so pure that a local brewery used it to produce beer, which was sold locally. The flooded part of the mine remains the largest reservoir of spare drinking water in the area.

FROM 1995, GUIDED TOURS were organised in the dry part of the Malogne mine, so that people could find out how their ancestors worked in the past.
The tunnels – which total some 160 miles – and caves were also examined by palaeontologists, who discovered the remains of prehistoric animals.
The mines of Mons are perfectly camouflaged by the landscape, and you need to be well prepared before embarking on a dive through its many miles of flooded tunnels.
It wasn’t easy finding someone suitable to guide us but eventually Kevin Haeke, an experienced cave-diver, offered to help. It was a hell of a job getting all our diving equipment to the entry point, and once there we took our time to prepare and test our rebreathers. I planned to carry out the first dive without a camera so that I could concentrate on reconnoitering the area for a later visit.
After a final check we start the dive, and I followed Kevin into what for me was unfamiliar terrain.
At first the visibility was bad, but the further we swam from the entry-point the clearer it became, until eventually it turned crystal-clear.
The first part of the tunnel was fairly narrow, but after the first right-hand corner the space became much larger. Over the first 100m of our exploration we encountered many objects that would have been used by the miners.
A third team-member had started paying out a guideline from the entrance to ensure that we would be able to find our way back there.
One of the advantages of phosphate over slate from a diver’s perspective is that the walls have a much lighter yellow and orange colour. However, this light colouring did give us the impression that the visibility was much better than it was.
After a while we noticed several side-tunnels to left and right. Each of these also had its own side-tunnels heading off in different directions.
It quickly became apparent that we would have to be very careful with the guideline to avoid getting lost in this labyrinth, which was about 3km long by 450m wide.
It took almost 40 minutes’ finning before we reached an area where we could poke our heads above the surface, revealing another exit. After a short break I was guided safely back to the entry-point by my two guides.
The dive had left a deep impression on me, and I planned to return as soon as possible with my camera. I soon found some good diving friends willing to join me on a photo excursion to the phosphate mine of Mons.
Stefan Panis and Karl Van Der Auwera are regular dive-buddies and Michael van Dijck had lots of cave-diving experience. In advance of the second dive I spent half a day preparing my camera and readying the flash units.
Stefan and I would be diving with APD Inspiration rebreathers and the other two divers would be using open-circuit.
Our intention was to light up as much of the long tunnels as possible, using remotely operated flashlights. We would head towards the clearest part ot the mine and take the photographs there.
Michael's assignment was to guide us safely back to the entry-point and not lose sight of the guideline. I would be too occupied with the photography to pay attention to the guideline, so Michael was my safety-diver.

SEVERAL MINUTES after leaving we reached the clear water and I started to shoot. We had agreed not to swim too close to the bottom, so as not to disturb the sediment and reduce visibility.
On this second dive I could see that the height of the main tunnels was at least 6m and they were 4m wide. At some points the struts designed to prevent collapse were still visible. And in several places the iron tracks of the mining carts and locomotives were still recognisable.
Keenly aware of how easy it would be to become lost in this maze we paid keen attention to the placing of our markers. After a 500m swim we decided to return, scoping some of the side-tunnels on the way back. These were much lower than the main ones, and gave the impression that some had been dug above each other.
After some final shots we returned to the starting point, trying to form a mental image of the numerous tunnels of this underwater city. Surfacing at the exit after more than 80 minutes all the divers were euphoric about this dive-spot. It would take many more diving hours to map this beautiful, enigmatic place.