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A record-breaking hole dug deeper into the Earth than the height passenger aircraft fly above it was eventually sealed shut after scientists reported hearing a "sound like hell".

The Kola Superdeep Borehole SG-3 in Russia was the product of a scientific Cold War race between the Soviets and the USA to acheive new feats in underground exploration. In 1989, just a few

years before the collapse of the Soviet Union, the Communist nation won the battle by reaching a staggering depth of 7.6 miles, or 40,230 feet, at a site in the Pechengsky District of the

Kola Peninsula, close to the border with Norway. The borehole remains the furthest mankind has ever delved towards the centre of this planet, and scientists made some remarkable discoveries

on the way. At the deepest depths of the hole temperatures of the surrounding rock reached an astonishing 180C, around double the heat researchers had predicted. On average the distance to

the molten core of the Earth is around 4,000 miles, which is still a lot deeper than the Soviets, or anyone else, has so far managed to dig. Extreme temperatures reaching above 4,000C at the

centre of the planet mean that getting close to anywhere near those depths and pressures is beyond the technology available today. But scientists did make some interesting discoveries in

Russia, including that water could be found nearly four miles down, and beyond that a layer of superheated mud existed. The researchers also found evidence of microscopic fossil life forms

dating back billions of years. Local reports also claimed the super deep hole emitted a chilling sound which could be picked up by scientists and people living nearby to the chasm-like pit.

After the end of the Soviet Union, funding for the 23-centimetre wide hole dried up and by 2007 the buildings and research station had fallen into ruins. Today a metal lid has been welded

over the hole to prevent anyone, or thing, falling down it. Reports a sound was heard from the hole are disputed, with some claiming apparent scream-like noises were actually created

afterwards from recordings from a horror film. The first account of a sound being reported to have been heard by researchers at the hole was broadcast by a US-based Chrisitan TV station. The

area does remain a tourist attraction, although visitor numbers have fallen since the Russian invasion of Ukraine.