Pluto's 'Gate to Hell'

The site, in the ancient Phrygian city of Hierapolis, now Pamukkale in southwestern Turkey, is said to closely match historical descriptions of what was known as Ploutonion in Greek and Pluutonium in Latin.

Describing the site, the Greek geographer Strabo (64/63 BC -- about 24 A.D.) said: 'This space is full of a vapor so misty and dense that one can scarcely see the ground. 'Any animal that passes inside meets instant death. I threw in sparrows and they immediately breathed their last and fell.'