While Cybele was a Phrygian goddess that made the migration into Roman mythology, the legend of Hades (Pluto) and Persephone (Proserpina) comes to Hieropolis from Greece. You know the story, Hades kidnaps Persephone and carries her into the underworld, allowing her to resurface only a few months of each year — as the birth of spring. Hieropolis’s many temples to gods and goddesses of Hell reference the Plutonium, an outlet for volcanic gases located near the hot springs. These heavy fumes frequently suffocated animals and people, which is why the vent was thought to be the gate to the underworld.