The efforts of St. Philip resulted in the foundation here of one of the first Christian communities and one of the first Christian churches. After Philip's I crucifixion by the Romans in 80 his son continued the work of proselytism. Although it would seem reasonable to assume that St. Philip was buried on the site of the ruins of this martyrium no trace has been found of his grave.
The martyrium itself is an octagonal structure on foundations measuring approximately 20 x 20 m. Access to the martyrium is afforded by a monumental flight of steps leading up to the building on the side towards the city. The imposing remains of the martyrium constructed in the first half of the 5th century in memory of St. Philip can be seen on slightly higher ground just outside the city defence walls.
The Martyrion was the most important Christian cult building at Hierapolis. The structure is composed of a central octagonal room. Eîght rectangular rooms open onto it, each with three arches supported by columns on marble octagonal plinths. The number eight which lies at the base of the entire complex architectural geomtry has a strong symbolic signifance. The arches bear Christian symbols within circles.
The central room, once capped by a wooden dome, contains a synthronon. The complex church plan was included in a square, which is surrounded by 32 rooms aligned along the sides. The building must have held earthly remains of the Apostle Philip. The Martyrion was built in early 5th century A.D. perhaps by an architect from the court of Constantinople.