Peel Castle was originally constructed by Vikings. The castle stands on St Patrick's Isle which is connected to the town by a causeway. It is open to visitors during the summer.
The castle was built in the 11th century by the Vikings, under the rule of King Magnus Barefoot. While there were older stone Celtic monastic buildings on the island, the first Viking fortifications were built of wood. The prominent round tower was originally part of the Celtic monastery, but had battlements added at a later date. In the early 14th century, the majority of the walls and towers were built primarily from local red sandstone, which is found abundantly in the area. After the rule of the Vikings, the castle continued to be used by the Church due to the cathedral built there – the see of the diocese of Sodor and Man – but was eventually abandoned in the 18th century.
The castle remained fortified, and new defensive positions were added as late as 1860. The buildings within the castle are now mostly ruined, but the outer walls remain intact. Excavations in 1982-87 revealed an extensive graveyard as well as the remains of Magnus Barefoot's original wooden fort. The most spectacular finds were the 10th century grave of 'The Pagan Lady' which included a fine example of a Viking necklace and a cache of silver coins dating from about 1030. The Castle's most famous 'resident' is the so-called Moddey Dhoo or 'Black Dog' ghost.
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.