Known as Pluto's Gate -- Ploutonion in Greek, Plutonium in Latin -- the cave was celebrated as the portal to the underworld in Greco-Roman mythology, and Italian archaeologists announced this month that they found it.
Unveiled at a conference on Italian archaeology in Istanbul, Turkey, the finding was made by a team led by Francesco D'Andria, professor of classic archaeology at the University of Salento.
Historic sources located the site in the ancient Phrygian city of Hierapolis, now called Pamukkale, and described the opening as filled with lethal vapors.
“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 BCE -- 24 CE) wrote. “I threw in sparrows and they immediately breathed their last and fell,” he added.
“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 told Discovery News.
The site also has the remains of a temple, a pool and a series of steps placed above the cave. Ionic columns at the site had inscriptions with dedications to Pluto and Kore, deities of the underworld.
Pilgrims took the waters in the pool near the temple, slept not too far from the cave and received visions and prophecies, as the fumes coming from Hierapoli's phreatic groundwater produced hallucinations. Priests sacrificed bulls to Pluto and pilgrims were given small birds to test the lethal effects of the cave.