Kola Superdeep Borehole

The Kola Superdeep Borehole is the result of a scientific drilling project of the Soviet Union in the Pechengsky District, on the Kola Peninsula. The project attempted to drill as deep as possible into the Earth's crust. Drilling began on 24 May 1970 using the Uralmash-4E, and later the Uralmash-15000 series drilling rig. Boreholes were drilled by branching from a central hole. The deepest, SG-3, reached 12,262 metres in 1989 and is the deepest artificial point on Earth, as of March 2019. The borehole is 23 centimetres in diameter.
In terms of true vertical depth, it is the deepest borehole in the world. For two decades it was also the world's longest borehole in terms of measured depth along the well bore, until it was surpassed in 2008 by the 12,289-metre-long Al Shaheen oil well in Qatar, and in 2011 by the 12,345-metre-long Sakhalin-I Odoptu OP-11 Well .

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