Scientists Discover the Secret to Ancient Roman ‘Gate to Hell’

Two millennia ago, a small Greco-Roman temple in present-day Turkey awed and enthralled its residents. Just beyond its stone gate, in a grotto shrouded in a heavy mist, a strange force worked dark deeds: Bulls ushered inside would lie down and perish; the castrated priests in charge would emerge unscathed.

Was it the bloodthirsty will of Pluto, the god of the underworld? The supernatural power of the priests? New research published on Feb. 12 in the journal Archaeological and Anthropological Sciences suggests a far earthlier explanation to the cave’s mystery: noxious carbon dioxide.