Hierapolis is mentioned only once in the New Testament (Colossians 4:15) where Paul states that Epaphras was working there and in nearby Laodicea.
Early Christian tradition states that Philip, along with his daughters, settled at Hierapolis. It is probable that Philip the Apostle (= disciple of Jesus) is the actual person, although a confused tradition suggests that it was Philip the Evangelist (see his activities in the book of Acts).
Tradition also states that Philip was martyred and buried here at Hierapolis. On a hill northeast of the city a Martyrium—a memorial that was a focus of pilgrimage—was built in the fifth century AD. In July 2011, the excavator, Francesco D’Andria announced that he had discovered the very Tomb of Philip in the vicinity.
I have posted 18 high-resolution images of the Martyrium of Philip. Click Here to view.