Surrounded in mystery and tales of demons, the Well of Barhout in Yemen's east - known as the "Well of Hell" - is a little-understood natural wonder.
Closer to the border with Oman than to the capital Sanaa 1,300 kilometers (800 miles) away, the giant hole in the desert of Al-Mahra province is 30 meters wide and thought to be anywhere between 100 and 250 meters deep.
A Turkish man who presents himself as a "bioenergy expert and metaphysicist" has triggered a social media storm after he posted a video claiming that it shows a "jinn."
40% of Bulgarians believe there is a secret society that governs the world. 29% of Bulgarians believe in the existence of aliens, 19% are convinced that people have contacted them, and 14% - that aliens live among people.
This shows a study of the Bulgarians' attitudes towards beliefs, conspiracy and superstition, carried out by Trend Research on the order of 24 hours newspaper.