Commentary Inf XXVII 94-97

In the fourth century Constantine, suffering from leprosy, had Pope Sylvester I brought to him from his cave on Soracte (where he was in hiding because of Constantine's persecution of Christians) to cure him. When the pontiff did so, Constantine converted to Christianity (and ended up in paradise, according to Dante [[Par XX 55-60]]); but he also out of gratitude was reputed to have given Sylvester authority over the western empire, centered in the city of Rome. (See C.Inf.XIX.115-117.)