Schloss Hollenburg is a medieval castle near Köttmannsdorf. It is on a rock of the northern slope of the Drava valley. One Swiker, Lord of Hollenburg in the Duchy of Carinthia was first documented as a witness in the 1142 deed of the foundation of Viktring Abbey. He may have been a liensman of the ducal House of Sponheim; his son Reginher is mentioned as Lord of Steuerberg, he accompanied King Conrad III of Germany on the Second Crusade in 1147 and later appeared as a ministerialis of Margarve Ottokar IV of Styria.
The castle was of strategical importance due to its location at a Drava river crossing and the road to the Loibl Pass and the March of Carniola. Upon the extinction of the Hollenburg dynasty in 1246, it passed to the Styrian Lords of Pettau, in 1438 it was inherited by the House of Stubenberg. The structure had been severely damaged by the 1348 Friuli earthquake.
In 1514 the Habsburg emperor Maximilian I, stuck in the War of the League of Cambrai against Venice and highly indebted, sold Hollenburg to Lord Siegmund of Dietrichstein, elevating him to the rank of a Freiherr (Baron). The House of Dietrichstein had the castle rebuilt in a Renaissance style, finished in 1588. The Dietrichsteins held the castle until the extinction of the branch in 1861, it was acquired by the Wittgenstein family in 1913.
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.