Costantine was a roman emperor from 306 till 337 A.D. He was one of the most important characters of the roman empire and his reign represented, especially for the christians, a fundamental moment. In fact, in 313 he issued the Edict of Milan with which he granted freedom of worship to the so far persecuted christians helping this way the spread of Christianism throughout the whole empire. Undoubtedly he was the first one to understand the importance of the new christian religion to strenghten the political and cultural cohesion of the empire. The Edict of Milan and his conversion were probably due because of political reasons but they had a great importance for the subsequent european history. Thanks to Costantine, many churches were built in Rome. Among them: S. Peter in Vatican, S. John in Lateran and S. Paul outside the Walls. Moreover, in 326, he founded the city of Costantinople (today Istanbul) that till 1453 remained the capital of the Bizantine Empire.