The Arch of Constantine was dedicated to the Emperor by the Senate and the People of Rome in A.D. 315. Constantine served as Emperor from A.D. 306 to 337. By the time of Constantine the church had made major departures from the New Testament pattern of church organization. The Emperor attended the Council of Nicea, but allowed the eastern bishops to preside over the meeting.
Grant comments on the question of Constantine’s conversion:
The question as to whether he was a “genuine” Christian or not depends on somewhat subjective definitions. (Encyclopedia of Early Christianity, 227).
The Arch of Constantine and the Colosseum. Photo by Ferrell Jenkins.
Helena, the mother of Constantine, was responsible for the construction of many of the well-known churches of the Holy Land. Rosenberg says,
Her role in church history was due to her partnership in Constantine’s program of church building at Bethlehem and Jerusalem and to her discovery of what she believed to be the true cross, both of which led to the revival of Jerusalem and the encouragement of pilgrimage to the Holy Land. (Encyclopedia of Early Christianity 417).
Ferrell's Travel Blog 
Nice photo and historical references, Thank you.
Honestly i had never heard of the Arch of Constantine, probably because the colosseum draws all the attention from it to itself.