It is situated partly over the Nymphaion (2nd cent. A.D.). The original floor-plan of the church was that of a cross, with apses on the four sides and a narthex on the west side. Four columns supported the dome. The altar and the floor were of marble. The disposition of tiles on the outer walls show "Cufic" decorative patterns of eastern origin. Four building phases are recognized, from the repairs and reconstructions over the years. Among the many mediaeval monuments known to have existed in the Agora, it is the only one preserved. It was restored to its original form in 1954-1957. The few surviving wall-paintings in the central aisle are of the 17th cent. Wall- paintings from other nearby churches have been placed elsewhere in the church.