‘Gate to Hell’ myths confirmed
Though Pamukkale, in western Turkey, is known for its travertines - limestone cliffs that have formed over 400,000 years from the mineral-laden water of nearby springs - an even more interesting attraction also calls the site home.
On top of the white towers sits the ruins of the ancient city of Hierapolis.
An ancient city
Founded by the Attalid kings of Pergamon at the end of the 2nd Century BC, Hierapolis was taken over by the Romans in 133 AD and turned into a thriving spa town.
The remains of the successful city are still visible, including its arched entrance gate, colonnaded main street and restored amphitheatre, all made from travertine.
“The thermal waters are likely one of the primary reasons for the city’s foundations,” said Dr Sarah Yeomans, an archeologist at the University of South Carolina who specialises in the Roman Empire.
“By the mid-2nd century, Hierapolis would have been a beautiful, bustling spa-town with what I imagine was a more dynamic and diverse population than most, given the popularity of such places with visitors.”
Truth behind the myths
Despite its beauty, Hierapolis was said to be the location of a “Gate to Hell”, a portal to the underworld where unsuspecting victims would be claimed by the hellhound Cerberus’ toxic breath on behalf of his master, the god Pluto.
A shrine was built on the site and pilgrims would pay priests to make sacrifices to the god Pluto on their behalf.
Writers at the time said priests would lead animals into the shrine and it would instantly drop dead, while the priest would return alive.
“I threw in sparrows, and immediately breathed their last and fell,” wrote the Greek geographer Strabo in Book 13 of his encyclopedia Geography.
Though visitors to the site today might find it hard to imagine these stories being true, one volcano biologist decided to test their validity.
“When I read the descriptions from the ancient writers, I began wondering if there could be a scientific explanation,” said Hardy Pfanz, who studies gases given off during geological processes at Germany’s University of Duisburg-Essen. “I wondered, could this Gate to Hell be a volcanic vent?”
To test his theory, Pfanz travelled to Hierapolis in 2013.
“We weren’t sure what we would find. It could’ve been made up, could’ve been nothing,” he said. “We most certainly weren’t expecting to get an answer so quickly.
“We saw dozens of dead creatures around the entrance: mice, sparrows, blackbirds, many beetles, wasps and other insects. So we knew right away that the stories were true.”
When Pfanz tested the air around the vent, he found the culprit: toxic levels of carbon dioxide. Where normal air contains 0.04 percent carbon dioxide, Pfanz found the concentration around the shrine reached 80 percent.
“Just a few minutes exposure to 10 percent carbon dioxide can kill you,” he explained, “so the levels here are really deadly.”
But Pfanz still had one question: if the area is so deadly, how did the priests in the shrine survive?
Returning a year later, he then studied the concentration of the gas over the course of the day, finding that it would quickly dissipate during the day when it was warm and sunny but would pool at ground level at night as the temperature decreased.
He came to the conclusion that the animals, with their noses close to the ground, quickly suffocated while the priests, standing taller, were breathing significantly lower levels of the gas and could survive.
Today, the shrine is bricked up and a walkway recently built around the site allows visitors to see the area without the risks of inhaling the deadly gas.
“When I first recognised that the legendary breath of Cerberus is actually carbon dioxide, I was standing right in front of the archway,” Pfanz said. “In that moment, I realised we had solved this ancient mystery; it was a really fantastic feeling.”
Image: Paul Cooper / Twitter