60 intrepid runners will take on an extraordinary challenge: to run the deepest marathon ever run. Covering 42.2km within the Garpenberg Zinc Mine in Sweden, they will descend to a staggering depth of 1,120 metres below sea level. No one has attempted a marathon at this depth before. Participants will endure temperatures of up to 30°C, in total silence and will be running in complete darkness with only their head torches for light.