The Cathedral Church of Saint German was built in 1879–84. The Patron of the Cathedral, St German of Man, was a Celtic missionary and holy man who lived from about 410 to 474.
The original cathedral of St German was inside the walls of Peel Castle and was built sometime in the 12th century when St Patrick's Isle was in the possession of Norse kings. At that time the church followed the Sarum Rite, prevalent throughout much of the British Isles. Around 1333 the Lords of Man refortified St Patrick’s Island and occupied the church as a fortress. In 1392 William Le Scroop repaired the Cathedral.
The building fell into ruin in the 18th century. After a considerable period of debate over who owned the ruins and site, it was decided not to rebuild that cathedral. The present building was constructed in 1879–84 to replace St Peter's Church in Peel's market place. In 1895, the bishop consecrated his chapel at the bishop's palace as pro-cathedral and instituted a chapter of canons with himself as Dean. That arrangement (bishop as dean) persisted even after the consecration of the new cathedral.
References:Rosenborg Palace was built in the period 1606-34 as Christian IV’s summerhouse just outside the ramparts of Copenhagen. Christian IV was very fond of the palace and often stayed at the castle when he resided in Copenhagen, and it was here that he died in 1648. After his death, the palace passed to his son King Frederik III, who together with his queen, Sophie Amalie, carried out several types of modernisation.
The last king who used the place as a residence was Frederik IV, and around 1720, Rosenborg was abandoned in favor of Frederiksborg Palace.Through the 1700s, considerable art treasures were collected at Rosenborg Castle, among other things items from the estates of deceased royalty and from Christiansborg after the fire there in 1794.
Soon the idea of a museum arose, and that was realised in 1833, which is The Royal Danish Collection’s official year of establishment.