(The Sun) – Earth’s deepest artificial hole stretches 40,000 feet below the surface – but it’s only covered by a rusty metal lid. Russia’s Kola Superdeep Borehole was created by the Soviets in the name of science so they could learn more about what’s really under our feet and dig to depths unknown. The project to drill into the Earth’s surface began near Murmansk in the 1970s, when Soviet scientists wanted to learn more about the Earth’s crust. Over two decades, they managed to dig more than 7.5 miles down into the Earth.

However, in 1992 they had to stop drilling because the temperature was around 180 degrees Celsius, which was far hotter than the scientists predicted it would be. Experts still need to figure out a way to overcome this temperature issue if they want to keep drilling and not destroy all of their equipment in the process. All this drilling wasn’t for nothing though as some scientific discoveries were made. The researchers found out that there is water at 12 kilometers into Earth’s crust, despite this previously being thought to be impossible. CONTINUE