Historic sources located the site in the ancient Phrygian city of Hierapolis, now called Pamukkale. A cave where the ruins were located emits dangerous gases as the ancient gate was said to be filled lethal mephitic vapors, according to historical sources.
The Greek geographer Strabo in 63BC mentioned about this cave: “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,”
A team of archaeologists led by Italian Professor Francesco D'Andria made the discovery, and it was announced at a conference in Istanbul last month. D'Andria has conducted extensive archaeological research at the World Heritage
Site of Hierapolis. Two years ago he claimed to discover there the tomb of Saint Philip, one of the 12 apostles of Jesus Christ.
D'Andria also found the remains of a temple, a pool and a series of steps placed above the cave -- all matching the descriptions of the site in ancient sources. D'Andria said: “People could watch the sacred rites from these steps, but they could not get to the area near the opening. Only the priests could stand in front of the portal. 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”
Private Tours of Pamukkale from Kusadasi