Grønsalen or Grønjægers Høj is about 100 metres long and 10 metres wide, which makes it Denmark's largest long barrow and is widely recognised as one of Europe's outstanding ancient monuments. The barrow, rising over a metre above the surrounding area, is encircled by 134 large stones. The grave, at the centre, is covered with earth and contains three burial chambers, two of which are open. It is not known when they were first opened or what was found inside. The long barrow was examined in 1810 by Bishop Münter and was protected by law after that. On the basis of its shape, the barrow has been dated as Neolithic, approximately 3500 BC. The first historical reference to the site was in ca. 1186 when it was called Grónesund.
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.