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.
In 1870 and 1874 it was demolished: only the three round towers, the so-called Three Acorns, and the foundation walls, uncovered in 1991, remained in good condition. Here are also the “Musée d’Art Moderne Grand-Duc Jean”, built after the plans of the Sino-American architect Ieoh Ming Pei and the "Musée Dräi Eechelen".