Scientists unravel the mystery of the Roman 'gate to hell'

By Nell Lewis, for CNN

Updated 2119 GMT (0519 HKT) March 9, 2018

Scientists believe they have figured out the mystery behind a Greco-Roman temple where animals were reported to drop dead as part of a ritual sacrifice. Known as the "Plutonium," the temple consisted of a stone doorway that led to a cave-like grotto, established around 190 BC. A team of Italian archaeologists rediscovered the cave in 2013 -- this is their 3D virtual reconstruction of the site.
Photos: The science behind the Roman 'gate to hell'
Scientists believe they have figured out the mystery behind a Greco-Roman temple where animals were reported to drop dead as part of a ritual sacrifice. Known as the "Plutonium," the temple consisted of a stone doorway that led to a cave-like grotto, established around 190 BC. A team of Italian archaeologists rediscovered the cave in 2013 -- this is their 3D virtual reconstruction of the site.
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These are the present-day remains of the Plutonium, in Hierapolis. In ancient times it was believed to be the gateway to the underworld as animals, led into the cave by Roman priests, would die of asphyxiation. The phenomenom continues today, as small birds and beetles have been found dead at the same site.
Photos: The science behind the Roman 'gate to hell'
These are the present-day remains of the Plutonium, in Hierapolis. In ancient times it was believed to be the gateway to the underworld as animals, led into the cave by Roman priests, would die of asphyxiation. The phenomenom continues today, as small birds and beetles have been found dead at the same site.
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During excavation, archaeologists found evidence of benches surrounding the Plutonium -- as this 3D virtual reconstruction shows. Visitors could watch the animal sacrifices, at a safe distance from the cave. New research shows that a fissure in the earth's surface, deep beneath the cave, emits carbon dioxide at such high levels that it can be deadly.
Photos: The science behind the Roman 'gate to hell'
During excavation, archaeologists found evidence of benches surrounding the Plutonium -- as this 3D virtual reconstruction shows. Visitors could watch the animal sacrifices, at a safe distance from the cave. New research shows that a fissure in the earth's surface, deep beneath the cave, emits carbon dioxide at such high levels that it can be deadly.
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