The Mponeng Gold Mine in South Africa is not your usual mining spot. It goes down about 4 kilometers—roughly 2.5 miles—under the Earth’s surface. That’s twice as deep as the Grand Canyon. Each day, nearly 4,000 miners descend in elevators that travel half a mile per minute. The first drop alone is 1.6 miles deep. After changing lifts, miners walk or drive to the lowest levels, getting closer to the Earth’s core than most people ever will. Deep underground, heat is extreme. Temperatures can reach 140 degrees Fahrenheit. To handle this, engineers pump ice slush mixed with salt down from the surface. Fans blow air over the ice to cool the tunnels to about 86 degrees Fahrenheit, creating an artificial underground climate. Mponeng is in South Africa’s Gauteng Province, in the Witwatersrand Basin. This area holds the world’s largest gold reserves. Almost half of all gold ever mined by humans came from here. The gold rush here helped found Johannesburg and changed South African history. Every day, the mine extracts about 6,000 tonnes of rock. In 2022, Mponeng produced nearly 200,000 ounces of gold after processing. Experts expect the mine to stay active until around 2029 if it remains profitable.