According to tradition, the Benedictine abbey of Herrenchiemsee was established about 765 by Duke Tassilo III of Bavaria at the northern tip of the Herreninsel. New findings however indicate an even earlier foundation around 620-629 by the missionary Saint Eustace of Luxeuil.
In 969 Emperor Otto I consigned the abbey to the Archbishops of Salzburg, who in about 1130 re-established Herrenchiemsee as a monastery of Canons Regular living under the Augustinian rule. In 1215, with the approval of Pope Innocent III, Prince-Bishop Eberhard von Regensburg made the monastery church the cathedral of a diocese in its own right, the Bishopric of Chiemsee, including several parishes on the mainland and in Tyrol.
In the course of the German Mediatisation, Herrenchiemsee Abbey was secularised in 1803 and the Chiemsee bishopric finally dissolved in 1808. The island was then sold; various owners demolished the cathedral and turned the abbey into a brewery. Plans for the complete deforestation of the island were blocked by King Ludwig II, who acquired Herrenchiemsee in 1873. He had the leftover buildings converted for his private use, the complex that later became known as the 'Old Palace', where he stayed surveying the construction of the New Herrenchiemsee Palace.
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.