For the next 24 years, they drilled on and off into the Earth’s crust. The result was the Kola Superdeep Borehole and a drill-depth of more than 7.5 miles (12 kilometers). To put that in perspective, Kola descends further than the deepest point of the ocean, which lies at nearly 6.8 miles (11 kilometers). The borehole is located on the Kola Peninsula of Russia.