Schloss Leonberg was founded in 1248 by count Ulrich I of Württemberg. The original castle was modified between 1560 and 1565 by the master builder Aberlin Tretsch by order of the duke Christoph. The widow of Frederick I of Württemberg, Duchess Sibylla (1564-1614), used the castle from 1609 as a widow's residence. Later, the castle was still repeatedly used as a residence. The castle today is a tax office.
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.