A Unique Challenge: The World’s Deepest Underground Marathon

In October 2025, a unique marathon took place in the Garpenberg zinc mine in Sweden, located 1,120 meters below sea level, making it the world’s deepest marathon. The event attracted 55 participants from 18 countries, including James Mason, who had not competed in a marathon for over a decade. The race was organized by Mason's company, reigniting his passion for running after years of focusing on family and career. The underground setting presented a distinct challenge, with participants running in a tunnel that was five meters wide and stretched over a mile.

The Guardian

Participants were required to adapt to the unusual conditions of the mine. The temperature was maintained at approximately 24°C due to geothermal energy and mining machinery, but the humidity was a stifling 72%. Runners were equipped with headlamps and helmets, as the tunnels were mostly unlit, and headphones were prohibited for safety reasons. Mason trained in the dark to prepare for the race, which added to the challenge of navigating the monotonous grey walls of the mine.

The Guardian

The marathon required runners to complete 11 laps to cover the full distance. As the race commenced, Mason experienced a mix of excitement and nervousness, particularly due to the oppressive darkness and the sound of machinery echoing through the rock. Initially, the atmosphere was lively, with participants encouraging one another. However, as the race progressed, the solitude and repetitive scenery became mentally taxing. Mason noted that the first 20 miles were manageable, but the final six miles tested his endurance.

The Guardian

Despite the challenges, Mason finished the marathon in first place with a time of three hours and 17 minutes, an outcome he had not anticipated. The camaraderie among participants was a highlight of the event, as they celebrated together after the race, congratulating the final runner and sharing a meal. All participants walked away as Guinness World Record holders, marking a memorable achievement in a unique setting.

The Guardian

Mason expressed his surprise and joy at winning, stating, “I had never expected to win.” He emphasized the significance of the experience, noting the unique camaraderie shared among the runners. The event not only tested physical limits but also fostered a sense of community among diverse participants.

The Guardian

• “I’m surprised,” a colleague said. “You do realise it’s totally underground?” — James Mason

The Guardian

• “But the biggest challenge was the monotony of those unending grey walls.” — James Mason

The Guardian

• “I was amazed: I had never expected to win.” — James Mason

The Guardian

This marathon exemplified how unconventional settings can create extraordinary experiences, blending personal achievement with a shared sense of accomplishment among runners from around the globe.

The Guardian