Siberia, Russia: Camera inside the first giant crater in Yamal - which literally means 'end of land' - shows walls like a moonscape and a silent, icy lake at the bottom.

This is what it is like inside the giant hole at the 'end of the world'.

With walls resembling a moonscape and an icy lake at the bottom of the 70-metre pit, no wonder scientists are baffled.

The first 80-metre wide crater which appeared on a Siberian peninsula called Yamal - literally meaning 'end of land' - sparked off a huge debate over what caused it.

Theories included a meteorite hitting earth, collapsing rock, global warming and even the idea it could be where a UFO crash-landed on Earth.

The last one sent believers in extra-terrestrial life into overdrive which has led this video to be viewed over seven million times already.

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But scientists from the Institute of the Earth Cryosphere, which sent in this camera to have a look at what was going on, believe a more natural cause is likely.

They think the hole was caused by the melting of underground ice in the permafrost, freeing gas that then built up high pressure and broke through to the surface.

Two new holes have appeared in northern Russia since this one, the first also on the Yamal Peninsula but the second hundreds of kilometres away in the Taymyr Peninsula.

Both were discovered by reindeer herders who almost fell into them as they worked in one of the remotest places on earth.

Chief scientist, Marina Leibman,said: “I have heard about the second funnel on Yamal, in Taz district, and saw the pictures.

“Undoubtedly, we need to study all such formations. It is necessary to be able to predict their occurrence.

“Each new funnel provides additional information for scientists."

Vladimir Pushkarev, the head of the Russian Centre for Developing the Arctic, said: "It's an interesting phenomenon.

“We are discussing further study of this place. It really is worth continuing scientific work.”

Scientists are taking soil and ice samples to find out when the holes were formed.