It was built in the 3rd century AD, Roman time. Classical architectural features which have large stone blocks were used in the construction. 

When the effects of Christianity had increased and accepted by everyone in Hierapolis in the 4th century AD, Roman baths were converted into a church. 

The pedestals are carved by Christianity symbols such as crosses etc. Walls were covered with marble slabs originally. 

Except from this converted church there are couples of more churches in Hierapolis.