Archaeologists working in Turkey have unearthed what they say is the entranceway to the underworld .... well, not literally. Instead, the archaeologists say the "Gate to Hell" that they discovered near the modern-day city of Pamukkale is the fabled Pluto's Gate, a site where oracles and priests would perform sacrifices to Pluto, also known as Hades, the god of the underworld.

The discovery was made by a team led by Francesco D'Andria, a professor of classic archaeology at the University of Salento in Italy, who two years ago also unearthed what he claimed was the tomb of Saint Philip the Apostle in a nearby location. The researchers were following historic texts that put the location of Plato's Gate in the ancient city of Hierapolis, which was built near the therapeutic hot springs in southwest Turkey beginning in the third century B.C. in the area that would later become Pamukkale.

According to ancient texts, the gate — or "Pamukkale" in Greek — contained deadly vapors that would kill any animal that entered the cave, yet certain priests could withstand the fumes. "We could see the cave's lethal properties during the excavation," D'Andria told Discovery News. "Several birds died as they tried to get close to the warm opening, instantly killed by the carbon dioxide fumes."

The site was mostly destroyed by earthquakes in the sixth century, but D'Andria says the research team found evidence of the temple that was originally built outside the cave, where Greco-Roman pillars and steps once led down into the toxic entrance to the Pamukkale itself. "People could watch the sacred rites from these steps, but they could not get to the area near the opening," D'Andria told Discovery News. "Only the priests could stand in front of the portal."

Hierapolis-Pamukkale was declared a UNESCO World Heritage site in 1988. Millions of tourists visit the site each year to see the ruins of Greek baths, temples and monuments.

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