Four groups of islands are in the parish of Cashel: the Black Islands; Clawinch, Priests' Island and Inis Clothrann. St Diarmuid founded a monastery on Inis Clothrann around 540 AD. On Saints' Island are the ruins of an Augustinian monastery that survived until the Dissolution of the Monasteries in the 16th century. A canon named Augustine McGradion (Uighistin Mag Ráidhin) compiled the Annals of Saints (Annales Prioratus Insulae Omnium SS) in this monastery in the 15th century. This island can now be accessed via a causeway.