The Vastseliina Castle was a castle of the Livonian Order, Bishopric of Dorpat. It was constructed in 1342 by the Landmeister Burkhard von Dreileben as part of the border fortifications of Old Livonia against Novgorod, Pskov and later Moscow. In the Middle Ages, Vastseliina Castle was well known in the Catholic world as a popular destination for pilgrims. They worshipped the holy cross in the castle chapel and a visit to the chapel gave them sanctification for 40 days – it was first validated by Pope Innocentius VI in 1354.
The castle met its end during the Great Northern War when it was demolished by Russian troops (1702). Today the ruins are open to the public.
Reference: Wikipedia, VisitEstonia
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.