Olbrück Castle is a hilltop fortress with a diamond-shaped floor plan. The central feature of the castle is the 34m high main tower, which dates back to the mid-14th century and is the oldest preserved part of the structure. Today, these rooms serve as museum spaces where visitors can learn about the construction history and function of castles. From the tower's roof, visitors have a panoramic view of the Rhine River to the east, the Ahr Mountains to the north, and the volcanic landscape to the south. On clear days, the Cologne Cathedral is even visible.
The castle was probably built originally in the 12th century. After several owners and reconstructions in the Late Middle Ages, During the Thirty Years' War, the castle was captured and devastated by Swedish troops in 1632. It was recaptured by Spanish and Electorate of Cologne troops under Graf Ernst von Isenburg-Grenzau in January 1633. Partially collapsed in 1660, the castle was subsequently restored under the supervision of Capuchin friar Bonitius from Linz.
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.