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 of Peel Castle during the 15th to 19th centuries.  The Fenella Tower is part of the 14th century defences.