Deepest nuclear explosion underground
Russian Federation (Nefte-yugamsk)
A 2.5 kiloton nuclear device was detonated at the bottom of a shaft 2,850 m (9,350 ft) deep at a location 60 km (37 miles) south of Nefte-yugamsk, Siberia, Russia, on 18 June 1985. The detonation was carried out in an attempt to stimulate oil production. For a comparison, the Hiroshima bomb had a yield of around 15 kilotons.

The Russians carried out 116 nuclear explosions between 1965 and 1988 in a program known as No. 7 - Nuclear Explosions for the National Economy. Known internationally as peaceful nuclear explosions (PNEs), their uses included reservoir and dam-building, mineral prospecting, increasing oil and gas production by liberating material from rocks, creating underground gas stores and putting out subterranean oil and gas fires. The United States had its own PNE program known as Project Plowshare.