The Classical-era city of Hieropolis was built to take advantage of the mineral baths at Pamukkale. It sprawls, widely scattered, over the plateau on top of the cliff, behind the Pamukkale Termal (the modern complex offering swimming and soaking pools under a roof, surrounded with expensive ice-cream and souvenir stands).
This is the Hieropolis theater. Unfortunately we made it to this part of the site too late in the day to explore much else. To explore Hieropolis thoroughly, you need time and good walking shoes.