The first historical mention of Gavnø is in King Valdemar's census book from 1231 where a 'house on Gavnø' is mentioned. The house was apparently a castle built to defend Denmark's western coasts. In the 15th century, Queen Margaret I opened St Agnes' Priory there, catering for nuns from aristocratic families. The chapel can still be seen in the castle's southern wing although it has since been extended.
In 1737, Count Otto Thott acquired Gavnø. He renovated and substantially extended the castle, creating today's three-winged, yellow-facaded building in the Rococo style where he was able to house his large collections of paintings, manuscripts and books. At his death, his library collection contained over 120,000 volumes, exceeding that of the Danish National Library. The park surrounding the castle is known for its rare trees, rose garden and, above all, its extensive display of bulbs.
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.