During the French siege of 1684, the French military engineer, Vauban, made the Porte-Neuve front the focus of the main attack on the Fortress of Luxembourg. Secondary attacks were carried out from the heights of Pfaffenthal and Grünewald, allowing the Bock to be bombarded and the Porte-Neuve front enfiladed. The few small earthworks constructed by the Spanish on the Grünewald heights were quickly removed by the French. After Luxembourg was taken, Louis XIV ordered the transformation and reinforcement of the fortress under the direction of Vauban. As a result, the crownwork on Pfaffenthal and the Parc hornwork were intended to prevent any besiegers accessing the plateau. In 1688, the Pfaffenthal and Parc redoubts were added to guard the approaches to these constructions.
In 1732/33, the Austrians built Fort Thüngen – named after the Oberstfeldwachtmeister Adam Sigmund VON THÜNGEN – on the site of the Parc redoubt. The new fort comprised an arrow-shaped redoubt enclosing an earthen core surrounded by a crenellated gallery approximately 1.8 m wide. The envelope surrounding the Parc redoubt is in the form of a detached bastion. The fort's defences were reinforced by a network of underground galleries and 71 mine chambers, many of which still exist today.
In 1836, under Prussian authority, the reduit was dug out to create 953 m2 of casemates that could house 400 to 500 soldiers. The three crenellated towers were added to the gorge, each crowned with a stone acorn. Hence their name in Luxembourgish: Dräi Eechelen (Three Acorns).
Following the Treaty of London of 1867, the dismantling of Fort Thüngen began in 1870. With the exception of the three towers and the first casemate, the demolished fort disappeared under a layer of earth and vegetation. Having been transformed into a park by the Parisian landscape designer, Edouard ANDRÉ (1840-1911), the Dräi Eechelen site became a place of recreation and relaxation for the people of the city.
The laws on the construction of the Museum of Modern Art Grand-Duc Jean on the envelope of the site and the Fortress Museum in the Thüngen redoubt, restored for this purpose, were voted in 1996.