In the year 1115, fortifications were erected at the site by Gosewijn I, Lord of Valkenburg. This original wooden keep survived until 1122 when it was destroyed under siege by Henry V, Holy Roman Emperor. The castle was rebuilt in the following centuries but was again destroyed in a siege, this time by Jan III, Duke of Brabant. The current ruins are those of the castle rebuilt in the 14th century.
The castle was blown up during the Franco-Dutch War, in 1672, by the army of King-Stadtholder Willem III to prevent it falling into French hands.
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.