Worrying reason the deepest hole in the world was sealed off

There's a massive hole in Russia that was once dubbed 'the entrance to hell'.

During the Cold War, the Soviet Union decided to build the deepest man-made hole to ever exist.

The ridiculously deep hole was nearby the Kola Peninsula in northwestern Russia, located by the border with northern Norway.

That's it. That's the hole. (Rakot13/Wikimedia Commons / CC BY-SA 3.0)

Known as the Kola Superdeep Borehole, drilling began on 24 May, 1970 up until 1992, shortly after the collapse of the Soviet Union.

The hole itself was actually made up of a number of other holes that are placed just off the central hole.

The deepest hole (sorry I know I'm writing 'hole' a lot) runs a whopping 40,230 feet into the Earth's crust.

That's the height of both Mount Everest and Mount Fuji put together.

You'd be amazed to know that the opening, however, is merely as wide as a dinner plate.

It was only for cash shortages and political circumstances that the hole project came to an end.

And it was for good reason to because temperatures at the bottom of the hole reached a terrifying 180C, which was a lot higher than predicted as tools were unable to cope.

The hole has since been abandoned.

Uli Harms of the International Continental Scientific Drilling Program, who worked as a young scientist on the German rival hole, told the BBC: “It was in the time of the Iron Curtain when the drilling was started.

“And there was certainly competition between us. One of the main motivations was that the Russians were simply not really open with their data.

Russia's hole was not sustainable. (LenorLux/Getty)

“When the Russians started to drill they claimed they had found free water – and that was simply not believed by most scientists.

“There used to be common understanding among Western scientists that the crust was so dense 5km down that water could not permeate through it.

“What was clear for the experience of the Russians was that you have to drill as vertical as possible because otherwise you increase torque on the drills and kinks in the hole.

“The solution was to develop vertical drilling systems.

“These are now an industry standard, but they were originally developed for KTB – and they worked until 7.5kms (4.7 miles).

“Then for the last 1.5–2km (.9 to 1.25 miles) the hole was off the vertical line for almost 200m.

“We tried to utilise some of the Russian techniques in the early 90s or late 80s when Russia became more open and willing to cooperate with the West.

“Unfortunately, it was not possible to get the equipment in time.”