The deepest hole ever drilled into the Earth's interior is the Kola Superdeep Borehole, located in the Kola Peninsula of Russia.

It reached a depth of 12,262 meters (40,230 feet), which is equivalent to 7.6 miles. However, this is still only a tiny fraction of the Earth's radius, which is approximately 6,371 kilometers (3,959 miles).

The drilling project started in 1970 and ended in 1992, with a few attempts to continue it in the years following.