The deepest hole ever dug was by scientists of the Soviet Union at the Kola Superdeep Borehole. The hole got to 40,230 ft (12.2km) deep, about 1/3 the way through earth’s crust and into the mantle. The Kola Superdeep Borehole was started in 1970 and halted in 1990 with the collapse of the Soviet Union. The whole point of all this drilling is to break through earth’s crust and bring up samples of the mantle.