The Heidetränk Oppidum near Oberursel is one of Europe"s most important Celtic oppida. The oppidum was surrounded by ramparts which encircled the settlement of opposite sides of a ravine called the Heidetrankthal. This imposing rampart where 10 km long and had six gates. The high point of the settlement was in the late La Tène period, but lost its importance in the mid first century BC. Archaeological finds from the Heidedtrank Oppidium include agricultural implements such as plowshares, hoes, scythe and sickle blades as well as tools and Celtic coins, particularly the so-called 'Nauheim Quinarius', which was probably coined in the oppidum itself.
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.