[1] The oldest surviving parts of the church building date from at least the 4th or 5th century; these include some pieces of floor mosaics, and traces of frescoes on the right side of the altar.

The tunnel inside which opens to the mountainside is thought to have served the Christians for evacuation of the church in case of sudden raids and attacks.

Water which seeps from the nearby rocks was gathered inside to drink and to use for baptism; the flow of this water, which visitors drank and collected to give to those who were ill (believing that it was healing and curative), has lessened as a result of recent earthquakes.

The side is also identified as such by Wilbrand of Oldenburg who visited it in 1211 and said that it was built over the house of St. Luke the Evangelist.

The remains to the left of the entrance belong to colonnades which formerly stood in front of the present facade.