Pope Sylvester baptises Constantine by immersion, having miraculously cured him from leprosy. One of the cycle of 13th century frescoes in the basilica S.S. Quattro Coronati Rome, purporting to illustrate a decree issued by Constantine in the 4th century, which, after recording his conversion to Christianity, supposedly conferred his temporal powers to the pope and bequeathed Rome and the western part of the Roman Empire to the bishop of Rome and his successors. In the 15th century this document was exposed as one of the great forgeries of the Middle Ages. It probably dates from the 8th century, but it was often cited in the conflicts between the papacy and the secular powers of the 11th and 12th centuries.