Pluto’s Gate, Turkey
It’s easy to understand why individuals in the past thought that Ploutonion in Hierapolis, also known as Pluto’s Gate, was a perilous location that may result in one’s death. It was constructed on top of a cave that was a sacred passageway to the underworld and produces deadly vapors, including high quantities of carbon dioxide. The fact that it was created as a religious site dedicated to the god Pluto and used as a ritual passage to the underworld seems fitting because, in 1965, scientists confirmed that it had been built on top of the cave.

Plutos Gate Turkey
