In ancient times, Pluto's Gate (Ploutonion in Greek, Plutonium in Latin) was a place most people would go to any length to avoid; it held a considerable importance in their mythology, celebrate as the gate to the underworld - Pluto being the Roman name for Hades.
“This space is full of a vapor so misty and dense that one can scarcely see the ground. Any animal that passes inside meets instant death,” the Greek geographer Strabo (64/63 BC -- about 24 A.D.) wrote. “I threw in sparrows and they immediately breathed their last and fell,” he added.
Archaeologists have often wondered what the exact location of this 'Gate to Hell' really is, but now, an Italian team working in Turkey seem to have convincing evidence that they've found the place. The finding was made by a team led by Francesco D'Andria, professor of classic archaeology at the University of Salento. D'Andria and his team conducted extensive archaeological research at the World Heritage Site of Hierapolis. Two years ago, he took a big step in the spotlight, when he claimed to discover there the tomb of Saint Philip, one of the 12 apostles of Jesus Christ - so far, that has neither been proved nor disproved.
Founded around 190 B.C. by Eumenes II, King of Pergamum (197 B.C.-159 B.C.), Hierapolis was famous for its hot springs, and the entire city was probably founded as a thermal spa. It also held a big theater and several significant temples. As it was conceded to Rome in 133 BC, it fluorished into a thriving city, with even more temples.
“We found the Plutonium by reconstructing the route of a thermal spring. Indeed, Pamukkale' springs, which produce the famous white travertine terraces, originate from this cave,” D'Andria said.
According to him and ancient writings, there was a mixed touristic/religious organization surrounding the area. Small birds were given to pilgrims to test the deadly effects of the cave, while hallucinated priests sacrificed bulls to Pluto/Hades. If you crossed the cave, you entered his dark realm of the underworld - from which there was no crossing back -unless you were Hercules or another hero.
“We could see the cave's lethal properties during the excavation. Several birds died as they tried to get close to the warm opening, instantly killed by the carbon dioxide fumes,” D'Andria said.
Still, there was a select group who could enter the cave - the eunuchs of Cybele, an ancient fertility goddess.
“They hold their breath as much as they can,” Strabo wrote, adding that their immunity could have been due to their "menomation," “divine providence” or “certain physical powers that are antidotes against the vapor.”
However, during the 6th century A.D., the Plutonium was obliterated by the Christians.