40,000ft view
Kola Superdeep Borehole
The deepest penetration of the Earth’s surface is the Kola Superdeep Borehole in Russia at 40,230 feet. Originally a Soviet project and a source of pride for the USSR, the aim was simply to drill as deep as possible into the Earth’s crust. The borehole is 9 inches in diameter. The project began in 1965 and terminated in 1995 when unexpectedly porous rock and high temperatures at this depth (356oF) made drilling unfeasible.
The Kola Borehole gave rise to the “Well to Hell” urban myth about scientists accidentally breaking through into a chamber of fire in Hell and hearing the sounds of demonic laughter through a microphone.
https://www.thomasnet.com/insights/how-deep-have-humans-drilled-into-the-earth-s-crust/