Was established in A.D. 324 by Emperor Constantine I (c. A.D. 272–337) was a Western Roman Emperor who, after a series of civil wars, became emperor of the entire Roman Empire. He strengt... more as the Eastern capital of the (27 B.C.) After a period of unrest and competing generals jockeying for power, Octavian, the adopted son of Julius Caesar, becomes the first official ... more. The city was built over the much smaller ancient city of Byzantium from which the Byzantium empire is named. After the fall of Rome in 476, Constantinople became the largest and wealthiest city in Europe. It rivaled Rome in importance in developing Christian theology and practice until its fall in 1453 to the Ottomans.