This stump of a tower marks the ruins of a substantial building that has played a major role in Antalya's religious life over the centuries. Built originally as a 2nd-century Roman temple, converted into the Byzantine Church of the Virgin Mary in the 6th century and then a mosque three centuries later. It became a church again in 1361 but fire destroyed most of it in the 19th century.
The ruins are fenced off but you can still see bits of Roman and Byzantine marble from the outside.