55 runners from 18 countries completed the World’s Deepest Marathon – setting
two new Guinness World Records and pushing human limits.
There are trail races… and then there’s the kinds of trail races that rewrite history. This is one of those.
Deep beneath the surface of the ground in Boliden’s Garpenberg zinc mine in Sweden, 55 runners from 18 countries gathered on 25 October 2025 to attempt something no one had done before: run a full marathon 1,120 metres below sea level, in the dark.
The depth of the marathon was one thing, but when you add in the other extreme variables, you have a race that tests a whole lot more than fitness; it tests nerve and resilience.
A Race Carved Out of the Earth
The format of the race was simple: 11 laps of a 3.84 km tunnel loop. But there was nothing simple about the conditions.
Because they were over 1 km below the surface, the runners had to push on without fresh air or a cooling breeze. To add to the challenge, humidity clung to everything, and temperatures soared close to 30°C. The ground was a mix of packed gravel and loose underfoot sections, so runners had to carefully navigate their way along the winding labyrinth of tunnels carved through the earth. And then there was the (almost) total darkness, disturbed only by headlamps, safety lighting, and the sound of 110 feet striking the earth in rhythm.
To run a marathon is challenging enough for any of us. But to run it over a kilometre underground, where the air is heavy and there is little reprieve from the heat, is something else entirely.
Yet every single participant pushed beyond the physical and mental challenges, finished and created history.
Running Deep But Running Safe
Boliden, the owner of the Garpenberg mine and a leader in safe, advanced zinc mining, hosted the World’s Deepest Marathon. Their team equipped runners with specialised safety gear and enforced strict protocols to keep everyone safe underground.
Mikael Staffas, CEO of Boliden, said: “We are immensely proud that, as one of the safest and most technologically advanced mines in the world, Garpenberg has hosted this world-record-breaking event. With outstanding air quality and cutting-edge technology making this feat possible…”
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More Than a Marathon
While the World’s Deepest Marathon was a remarkable feat in itself, it also had a deeper purpose.
So far the event has raised a staggering $630,000 for the BecomingX Foundation and the Wild at Heart Foundation, supporting global youth development and animal welfare initiatives.
The World’s Deepest Marathon was also a statement. It celebrated the resilience of the human spirit and showcased the transformation of the modern mining industry. Mining has become a place where innovation, sustainability and human endurance can intersect.
That innovation even extended into the digital world.
Minecraft creator Seapeekay livestreamed the game live from inside the mine, and jumping into the action himself by running a lap of the course.
A surreal collision of virtual mining, real-world mining and human endurance.
A Moment Recognised Around the World
Another first for the World’s Deepest Marathon is it’s place in the Guinness World Record books. It has now been officially certified as a Guinness World Record for both The Deepest Marathon and The Deepest Underground Marathon Distance Run (Team).
When Guinness World Records officially certified the achievement, BecomingX CEO Paul Gurney summed up what it meant:
“Setting not one but two world records is a testament to all of our runners who pushed themselves to their physical and mental limits in an environment few will ever experience — and who can now rightly call themselves world record holders!”
Beyond the Record Books
Trail runners love a frontier, a new challenge, a fresh landscape, a wild idea that pushes the boundaries of what running can be.
This marathon did exactly that.
It wasn’t scenic, or fast and it wasn’t designed to be like other marathons.
It was designed to test humans in a place built for machines.
To bring light into the dark.
To prove that adventure doesn’t always need altitude, sometimes adventure can be found in unusual places.
And for 55 runners, the finish line wasn’t just a place they reached; it became a place that will forever be etched in their psyche and recorded in history.
