The site of current Seeburg castle was mentioned first time in 740 AD. The construction of current castle was started in the 11th century (around 1036). It was largely extended by Wichmann von Seeburg, later Archbishop of Magdeburg (1115-1192). The next renovations took place in the 14th and 15th centuries, when the castle was flanked by towers and a gatehouse under the rule of Counts of Mansfeld.
Later Seeburg was left to decay until the Counts of Ingenheim sold it in 1880 to the Wendenburg family. In 1923, Erich Wendenburg commissioned the architect Paul Schultze-Naumburg to completely restore the building in neo-Gothic style.
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.