Fort Thüngen is a historic fortification in Luxembourg City sited in Dräi Eechelen Park. Named after the Austrian commander-in-chief of the fortress, Baron of Thüngen, it was built in 1732 to enclose the defence work called Redoute du Parc (Park Redoubt) set up by Vauban 50 years before. A deep moat surrounded Fort Thüngen which was accessible only through a 169-metre long underground tunnel through the rocks from Obergrünewald. In 1836 the Prussians extended the Fort and in 1860 strengthened it again.
Most of the original fortress was demolished after the 1867 Treaty of London, which demanded the demolition of Luxembourg City's numerous fortifications. The three towers and the foundations of the rest of the fort were all that remained. During the 1990s, the site was reconstructed in its entirety, in parallel with the development of the site for the construction of the Mudam, Luxembourg's museum of modern art.
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.