A popular health resort in classical times, Hierapolis had baths that could accommodate 1,000 bathers. Nearby are the dazzling travertine terraces at Pamakkule (Cotton Castle) made from the limestone deposits of hot springs.

Hierapolis has the largest necropolis in Anatolia, evidence that the spa attracted the sick and the elderly. The city founded by the Pergamum dynasty in the 2nd century BC was largely destroyed in an earthquake in AD60, and the ruins are principally Roman. On the east side of the agora are the remains of the Martyrium of Philip the Apostle, who was crucified here, upside down.

In 2013 an Italian arechaeolgy team found what they believe to be the Gates of Hell, a vapout-filled cave described by Strabo: “Any animal that passes inside meets instant death. I threw in sparrows and they immediately breathed their last and fell.”