The design of a new structure to replace the old ruined castle of Poppelsdorf commenced in 1715 at the request of the owner, Joseph Clemens, Archbishop-Elector of Cologne, who engaged the French architect Robert de Cotte. Clemens wanted a maison de plaisance that would be near his remodeled Bonn Palace one-half mile to the north. There was to be a canal between the two, following the example of the Palace of Versailles and the Trianon de Marbre.
Work came to a halt after Clemens' death in 1723, but his nephew and heir, Archbishop of Cologne Clemens August, undertook a second campaign of construction in 1745–1746.
Under the Prussian rule, in 1818 the Palace and the nearby Park became part of the University of Bonn. In the same year the Park was converted to the Botanical Garden of Bonn, which today contains about 0.5 hectares of greenhouse area with eleven greenhouses and about 8.000 different plants.
In 1944 the Palace was heavily damaged by an Allied air attack. It has been rebuilt in a much simpler appearance from 1955 on.
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.