A one piece carved marble, baptistery found in the St. Paul Church at Pisidian Antioch. It is inscribed with the name of St. Paul (not visible in photo). On the front of the baptistery is an inscribed cross.
Usually baptisteries from this period are larger and more permanent — being located outside of the church building proper. Speculation: might this instead be a receptacle for "holy water?"
The baptistery is displayed in the courtyard of the museum in Yalvac.