Question

The Emperor, always intent on the advancement of religion, erected splendid Christian temples to God in every place—especially in great cities such as Nicomedia in Bithynia, Antioch on the Orontes, and Byzantium. He greatly improved this latter city, and made it equal to Rome in power and influence; for when he had settled his empire as he was minded, and had freed himself from foreign foes, he resolved on founding a city which should be called by his own name, and should equal in fame even Rome.—Public Domain

Who is the emperor described in this excerpt?