St Patrick's Isle, encompassing an area of 7.5 acres, has been the focal point of ecclesiastical, military and secular occupation from the Early Christian to Medieval and later periods, which is attested by the standing remains and through excavation.


St German's Cathedral, possibly on the site of a predecessor, was founded in the 13th-14th centuries but due to the incursions of the raiding Scots was protected by a curtain wall and gatehouse in the later 14th century, a feature that was to develop into the fortress and garrison known as Peel Castle.