The Archbishops of Mainz had the Mildenburg castle built at the end of the 12th century to secure their powerful position and to serve as a customs office. Around 1200, the castle keep was added, the first official reference dates to 1226. Rather diverse periods in history affected the castle: extending, capturing, damaging and reconstructing.
Mildenburg the seat of the Oberamtmann, the Archbishop's local administrator until 1803. It then passed to the Princes of Leiningen before Carl Gottlieb Horstig purchased it in 1825. It now houses a museum of icons and contemporary art. The castle’s inner ward once held the Teutonenstein, a 5 m-tall sandstone column found on Greinberg, the inscription of which is still a puzzle to this day.
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.