Damascus, the Church of Saint John Baptist

With the advent of Christianity as the official creed of the Roman Empire, there was no longer a need for colossal temples attracting pilgrims from all over the country. Under the new faith numerous churches were built so each village and each quarter could have its own place of worship. The Temple of Jupiter of Damascus was modified accordingly as its peribolos lost its religious function and acquired instead a distinctly commercial character along with the new name of gamma since its shape resembled this letter of the Greek Alphabet. It was towards the end of the 4th Century AD under the emperor Theodosius that the temple of Jupiter was transformed to the Church of St. John. The tradition of the burial of Saint John the Baptist' s head at this location, however, is no older than the late 6th Century. The location of the main entrance to the church was in the southern wall (whereas that of the pagan temple was in the eastern wall) and it now is blocked. The only remnant of the Byzantine church is a Greek inscription over the blocked southern opening that is an adaption of Psalm 145.13: Thy Kingdom, O Christ, is an everlasting Kingdom, and Thy dominion endureth throughout all generations. 

The second figure represents the Church of St. John (currently the Umayyad Mosque) at the time of the Arab Muslim conquest according to F. Shafey.

Damascus: A History
Ross Burns
ISBN: 9780415413176

Early Muslim architecture by Sir K A C Creswell
Oxford University Press, 1969