Søborg Castle, in its heyday, was the strongest castle in Denmark, and was also used as a prison. It was inhabited until the Count's Feud in 1535, when it is speculated that it was destroyed. In 1577, the feudal tenant was granted permission to use the ruins as a quarry.
Søborg Castle is first known from the 12th century, when ownership of the castle passed from the king to the bishop of Roskilde. Traditionally archbishop Eskil of Lund is said to have expanded the previous buildings to a real castle with defensive walls and a moat. As Eskil was in close contact with Esrum Abbey, it is considered likely that he lived nearby at Søborgby.
In 1985, Robert Egevang and Søren Frandsen took the initiative of digging two trenches to make clear the conditions between the octagon tower and the castle proper. A rampart approximately 11 meters wide is the oldest encirclement of the castle. In the rampart, as well as in the octagon tower which was built at the same time, tiles have been found. The excavations show that the castle proper was erected in the late 13th century, which would make it unlikely that Eskil was the builder, as he died in 1181. The tiles are very unevenly made, evidence of their novelty in Denmark, after having only recently arrived from Lombardy.
In the Middle Ages, the castle was on an island in a fjord with an outlet to the Kattegat by Gilleleje. Later, the fjord became Søborg Sø, which was drained 1872-1896 when a canal was dug to Gilleleje.
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.