There has been a cathedral at the St Carthage’s site since the middle of the 12th century. This early cathedral had a tumultuous history, including its likely sacking during the Anglo-Norman invasion of the late 12th century and its damage, almost to ruins, during the Desmond Rebellion of 1579. The cathedral in its current incarnation was designed by Sir William Robinson and constructed from 1679 on. The present windows and doors date to the 19th century.

The Cotton Library, a fantastic collection of rare 16th- and 17th-century writings, is attached to the cathedral. Established by Henry Cotton circa 1851, the collection features a number of significant works from Cotton’s own library and, donated later, from numerous other sources. Among these works can be found early translations of the Koran and of John Calvin’s writings, as well as some of the works of local scientist and mathematician Robert Boyle. The library also contains a number of interesting curios. Unfortunately, the library is not regularly open for public viewing.