The Abbey of Kells was first founded by St. Columba ca. 554. What some historians term a refounding happened in the early ninth century by Columban monks fleeing from Iona which was repeatedly raided by the Vikings. The site was a former Irish hill fort. In 814, Cellach, Abbot of Iona, retired to Kells. After further Viking raids, the shrine of St Columba was transferred to the Abbey of Kells. Historians now believe that the Book of Kells may have been either started in Iona and finished in Kells or written entirely in Kells by successive generation of monks.