Constantine the Great was a Roman Emperor who ruled from 306 to 337 AD. He is best known for being the first Christian emperor and for establishing Constantinople as the new capital of the Roman Empire. His reign marked a significant shift in the empire's religious landscape, promoting Christianity and leading to the Edict of Milan in 313 AD, which granted religious tolerance. Helena was the mother of Constantine and played a crucial role in his life and reign. She is often credited with influencing his conversion to Christianity. Helena is also known for her pilgrimage to the Holy Land, where she is said to have discovered the True Cross, a significant relic in Christian tradition.