1. Edict of Milan: In 313 CE, Constantine issued the Edict of Milan, which granted freedom of religion throughout the Roman Empire. This was a major turning point for Christianity, which had previously been persecuted by the Roman authorities. The edict allowed Christians to worship freely and build churches, and it marked the beginning of Christianity's rise to dominance in the Roman world.
2. Moving of the capital to Constantinople: In 330 CE, Constantine moved the capital of the Roman Empire from Rome to a new city on the site of Byzantium, which he renamed Constantinople. This decision had several important consequences. It shifted the center of power away from Rome and towards the eastern provinces of the empire. It also led to the development of Constantinople as a major cultural and political center, and it became the capital of the Byzantine Empire after the fall of the western Roman Empire in the 5th century.