Have you ever tried digging in the beach sand a deep hole? what depth would make you proud?
This innocent metal plate covers the "Kola Superdeep Borehole".
"Kola Superdeep Borehole" is a hole drilled into the Earth's crust by the Soviet Union in 1970. In 1989 the hole reached depth of 12 Km! and earned the title "Deepest artificial hole on earth".
The drill stopped in 1994 because the hit down there reached more then 180 °C.
The hole is only 23cm diameter so no human can fall into, but if someone did, it would take 50 seconds of free fall to hit the bottom.
Source:
https://en.wikipedia.org/wiki/Kola_Superdeep_Borehole
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