Where Is the Deepest Mine on Earth?

Mponeng gold mine, operated by Harmony Gold, is located about 65 km southwest of Johannesburg in the Witwatersrand Basin of South Africa. Its deepest working levels reach approximately 4,000 metres (4 km) below the surface. At that depth, the rock temperature exceeds 60 °C, requiring massive refrigeration systems that pump ice slurry underground to keep working areas at a survivable 28-30 °C. Miners descend via a system of elevators and travel up to an hour to reach the working face. The mine produces gold from an ancient reef of gold-bearing conglomerate laid down about 2.7 billion years ago.