Byzantium was an old city. There had been a settlement on the banks of the Bosphorus since the 5th century BCE. Its strategic position guarding the strait from the Sea of Marmara to the Black Sea made it an important waterway for trade all the way from Western Europe to Asia.
By the time of Constantine the Great, it was being revamped into a commemorative treasure city, but circumstances in Rome changed. At the Battle of Milvian Bridge, Constantine underwent some sort of spiritual conversion. Eusebius describes it later as a vision of the Chi Rho symbol representing Christ. There is some doubt on this as it was no reference to it until much after. However, something did happen to make Constantine favorable to Christianity. He and his co-emperor issued the Edict of Milan, which granted Christians freedom to practice their religion. Constantine went about trying to turn Rome into a Christian city. He built the churches of S. Paulo fuori le Mura and S. Sebastiano, and most famously a basilica over the site at the Vatican where St. Peter was said to be executed. By the time he was sole emperor, he built a number of churches trying to turn Rome into a pilgrimage site for Christians. However the old guard wasn’t happy. They were not being forced to convert to Christianity, but it was strongly encouraged. They also did not like rumors of the gilded city Constantine was building on the Bosporus to bear his name. Despite living in a monarchy for centuries, they still thought of themselves the guardian of republican values. They were not going to change easily.
By his second visit to Rome, Constantine was positive the old ways and beliefs had no place in the new empire he was building. Intellectual and economic centers were moving east as well as threats to the empire that needed watching. Italy was falling victim to waves of malaria and the population was decreasing. It was time to move.
Since he was starting basically from scratch, the old settlement notwithstanding, Constantine could set the city up exactly as he wanted. There are legends that he drew the perimeter of the city walls with a spear, and his companions asked why so far, he replied, “I shall continue until he who walks ahead of me bids me stop.” However, despite the lack of angelic city planning, it was still an amazing city. At the center of the city was the Milion, or First Milestone, which was four triumphal arches forming a square. Set in the cupola held by the four arches was a fragment of the True Cross, brought back from Jerusalem by Constantine’s mother St. Helena. It was from this spot that all distances in the Empire were measured. To the east of the Milion was the first Christian church of the new capital, the Holy Peace of God, St. Eirene. Later this small church would be overshadowed by the larger more famous St. Sophia, the Church of Holy Wisdom. Running westward from the Milion was the Mesë, a wide avenue that led to a beautiful new marble forum at the center of which was a hundred foot column of porphyry from Heliopolis. Kept in the forum were the treasures of the Empire- the hatchet Noah used to build the ark, the leftover bread from when Christ did the miracle of the loaves and fishes and Mary Magdalen’s jar of ointment. From the ancient world was the figure of Athene brought back by Aeneas from Troy. To modern ears, this sounds ridiculous, but to the believers then it was very serious. At the pinnacle of the forum stood a statue of Constantine, with a sunbeam halo and a fragment of the True Cross in his hand, just in case you forgot whose city you were in.
Constantinople was dedicated to the Holy Virgin at the High Mass at St. Eirene during Emperor Constantine’s silver jubilee. Anyone who was anyone was flocking to the new city and leaving the old capital in the dust. It was May 11, 330, and a Monday, making Monday a lucky day in the Greek world up to present times.