Nassenfels castle dates from the 12th-13th century. The first reference to the castle is dated to 1245, when Count Gebhard III of Hirschberg was assassinated when he was besieging Nassenfels castle. The castle was reconstructed and enlarged later and the current appearance dates from c. 1400. The three towers were built by bishop Friedrich von Oettingen. Nassenfels was again restored in 1464 and 1699. in 1807 the castle was sold to private owners and used as a quarry.
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.