A cave in ancient Rome , which the Romans believed to be a true "door to hell," was so deadly that it had killed all the animals that had come close to her but had not killed the clergy who had led them. The mystery seems to be about to be revealed millennia later, after scientists think they have understood what the mechanism behind the ancient mystery is. In their view, this was actually a cloud of carbon dioxide that had suffocated those who had inhaled it.
The cave, aged 2200 years, was unveiled seven years ago by archaeologists at the University of Salento. It was located near a town called Hierapolis in ancient Phrygia on the territory of today's Turkey and was used for animal sacrifices, mainly bulls that were transported through Plutonium - or the door of Pluto, the ancient Roman god of the underworld, of castrated clergymen. Once the bulls were introduced to the arena, spectators could sit on the raised seats in the arena and watch the poisonous vapors that rise from the cave killing the animals.