Around 1076 Archbishop Gebhard of Salzburg, a follower of Pope Gregory VII in the Investiture Controversy, had the Petersberg fortress erected above the town in order to prevent Emperor Henry IV from crossing the Alps. The archbishop also had fierce enemies in the Carinthian ducal House of Sponheim, who after his deposition made several attempts to take possession of Friesach. Constant attacks by Duke Engelbert were finally repelled in 1124. In 1149 King Conrad III of Germany stayed at the castle on his way back from the Second Crusade, as did Richard the Lionheart returning from the Third Crusade in 1192, attempting to elude the guards of Duke Leopold V of Austria.
Today the castle is home to the Friesach City Museum, which features exhibits about the town's history, culture, mining industry and trade.
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.