Hachenburg Castle, former seat of the Counts of Sayn, was founded about 1180 by Count Heinrich II of Sayn. Building was finished in 1212 under Count Heinrich III, the founder's son, who was also mentioned as the town's and the castle's first owner. The castle church only arose in the late 15th century and underwent several remodellings until the 18th century.
In 13 October 1654, there was a great fire which burned down the inner town and also the castle. Counts Salentin von Manderscheid and Georg Friedrich von Sayn-Hachenburg undertook to build the town anew, and also the castle, although this time as a Baroque structure. The sweeping Baroque castle was built to architect Julius Ludwig Rothweil's plans between 1715 and 1746. It has had many owners over the last century. For a few decades, however, it has been the seat of Deutsche Bundesbank’s training centre and professional college.
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.