Probably built in the first half of the 12th century (although some legends say it was built in the 9th century), Sandiás Castle was located over a castrum (Celtic settlement). It participated in the Portugal secession wars (12th century). In 1386 it was assaulted by the duke of Lancaster, pretender to the Castile crown. In the 15th century it was demolished by a popular riot, and rebuilt later. It was a meeting point for troops in the wars with Portugal in the 18th century. There are many legends about this castle.
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.