The existence of the Fort Risban was first mentioned when it was besieged by the English in November 1346. Edward III of England's troops, finding the defences of Calais impenetrable, decided to erect a small fort to prevent any supplies reaching the town by sea, with a view to starving the inhabitants into submission. Under the English occupation the wooden tower was replaced by a stone structure, the Stone Tower, after 1400 renamed Lancaster Tower, a name often given to the fort itself.
Fort Risban was used by the English forces until 1558 when Calais was restored to France. In 1596, the fort was captured by the Spanish until May 1598 when it was returned to the French following the Treaty of Vervins. It was rebuilt in 1640. Vauban, who visited the fort some time in the 1680s, described it as 'a home for owls, and place to hold the Sabbath' rather than a fortification and let the fortress be altered. In the 19th century the Engineers Corps altered it again. The sea-fortress was dismantled in 1908 but fortified again during World War II when it served as an air raid shelter.
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.