The Bishop's Palace, Kirkwall was built at the same time as the adjacent St Magnus Cathedral. It was built for the cathedral's first bishop, William the Old of the Norwegian Catholic church who took his authority from the Archbishop of Nidaros (Trondheim). The ruined structure now looks like a small castle.
Originally it is thought to have been like a typical Royal Norwegian Palace, with a large rectangular hall above store rooms and a tower house as the Bishop's private residence. King Haakon IV of Norway, overwintering after the Battle of Largs, died here in 1263, marking the end of Norse rule over the Outer Hebrides. The neglected palace had fallen into ruins by 1320.
In 1468 Orkney and Shetland were pledged by Christian I of Denmark and Norway for the payment of the dowry of his daughter Margaret, betrothed to James III of Scotland, and as the money has never since been paid, their connection with the crown of Scotland has been perpetual. In 1526 the palace came briefly into the possession of William, Lord Sinclair, before he was ordered to return it to the Bishop of Orkney. When King James V of Scotland visited Kirkwall in 1540 he garrisoned his troops in the Palace and in Kirkwall Castle. Soon afterwards' extensive restoration was begun by Bishop Robert Reid, the last and greatest of Orkney's medieval Bishops who also founded the University of Edinburgh. Reid added a round tower, the Moosie Toor.
Ownership passed to Robert Stewart, 1st Earl of Orkney, in 1568, then to his son Patrick Stewart, 2nd Earl of Orkney who planned to incorporate it into his Earl's Palace, Kirkwall, but debts forced him to return it to Bishop James Law. Earl Patrick's son Robert seized both palaces in 1614, and a siege followed, though it is not known if this caused damage to the structures, both of which are now ruins.
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.