The most important and representative of the divinities of Hierapolis was Apollo. The Temple of Apollo was built on a cave where carbon dioxide emanated which gave it the adjective Plutonion.
Large steps lead one to the platform of the temple of a height of 2.5 m. A peribolos is surrounded in front of the temple measuring aproximately 20 m by 15 m The temple dates from IInd century .Artemis who was the sister of Apollo was adored here like in Ephesus. In a relief on the stage Artemis represented like the Artemis of Ephesus.
The cave where noxious gases emanate under the temple is consecrated to Pluto. Once upon a time priests went in accompanied by animals and came out of it (having breathed the fresh air which existed in intervals) unaffected.
They thus prided themselves of their power. This ''Hole of Djinns'' was marked dangerous.