Aerial view of the Well of Barhout, known as the "Well of Hell", in the desert of Yemen's Al-Mahra province.

Closer to the border with Oman than to the capital Sanaa 1,300km away, the giant hole is 30 meters wide and believed to be between 100 and 250 meters deep.

Local folklore says it was created as a prison for the demons, a reputation bolstered by the foul odors rising from its depths.