Those summer trail runs getting a bit too hot? I logged a ten-miler last week in Alabama, where I live, and it was so muggy I may have performed better if I’d been on a treadmill inside of a sauna.
This time of year, the thought of competing in a cool, underground race has its appeal.
That’s the idea proposed by BecomingX, a learning and development company co-founded by adventurer Bear Grylls. The organization, in partnership with the International Council for Mining and Metals, is hosting the world’s deepest marathon in the tunnels of a Swedish zinc mine called Garpenberg.
The marathon will be held on October 26, approximately 4,300 feet below the Earth’s surface. Sixty runners will don climbing helmets, safety glasses, hi-vis clothes, and headlamps as they take laps around a sprawling mine tunnel, all in complete silence and darkness. In addition to setting a Guinness World Record, the events’ organizers hope to raise at least $1 million for two charities: canine charity Wild at Heart and the BecomingX Foundation, which, according to its website, “helps disadvantaged students in underserved communities across Africa.”
“We’re incredibly proud to host this historic event at our Garpenberg mine,” said Mikael Staffas, President and CEO of Boliden, the company that owns the mine, in a press release on July 18. “As one of the safest and most technologically advanced mines in the world, it’s the perfect setting to show that mining can be both cutting-edge and purpose-driven. We look forward to welcoming the intrepid runners and shining a light on an industry that’s critical to a sustainable future.”
Garpenberg is one of the most productive mines in Sweden, and the source of around one percent of the entire world’s zinc concentrate. Annually, the mine extracts nearly 4 million tons of ores containing zinc, silver, lead, gold, and copper. Historical records show mining has been conducted on the site since at least 350 B.C.E.
Underground marathons have been around for quite a while. From 2002 to 2014, a marathon called the Untertage Sparkassen was held in a German salt mine, 1,640 feet below sea level. And last December, some 100 runners ran laps around a World War II-era bunker in the United Kingdom, in the country’s first underground marathon.
Other runners have covered long distances at far greater depths, though not as part of an official event. According to the Guinness Book of World Records, the deepest underground half-marathon distance was run at a staggering depth of 11,676 feet, by Ecuadorian Millán Ludeña inside of a mine in South Africa in 2017.
The Garpenberg race technically isn’t open to the public. The 60 runners are already confirmed, and all will be what the event’s released called “representatives from the mining and metals industry and civil society,” hailing from at least 17 different countries. According to the event’s website, “the majority will not have run a marathon before.” However, organizers at BecomingX say that if any registered runners cancel, a few slots may open up. The catch? You have to raise $30,000 in charity sponsorship to enter to help get them to their $1 million goal.

Even if you can drum up the cash and secure a slot, you’ll have other challenges to overcome. Organizers estimate that, depending on the weather above ground, temperatures inside the mine will range from 75 to 86 degrees Fahrenheit. There are also possible health risks when running underground, primarily due to the reduced ventilation, and a subsequent buildup of pollutants like particulate matter in the air, which can be hard on the lungs. A 2020 study in the journal Frontiers in Public Health notes that underground spaces, in general, are prone to “decreased oxygen concentrations and increased carbon dioxide concentrations, elevated humidity and temperature, increased toxic particle concentrations, and accumulation of radioactive radon.”
I’ll take my chances running in the sauna!