After the City of Luxembourg was taken by the French, Vauban was commissioned to draw up a plan to transform and reinforce the fortress, which he signed on 19 August 1684. He consolidated the defences with the inclusion of Pfaffenthal. The Grünewald heights were fortified to hinder the efforts of potential besiegers. A crenellated enclosure wall, broken by the Eich and Bons Malades gates, runs from the Berlaimont redoubt, crosses the Pfaffenthal and joins the Paffendal crownwork. From there, another gated wall runs along the Hoehl ravine to join the Parc hornwork then links up with the Mansfeld gate at the foot of the Bock. The Parc redoubt was added in 1688 to guard the approaches to the fort.
When the Austrians took possession of the fortress in 1716, the Parc hornwork became Fort Obergrünewald. When Fort Thüngen was built, an underground gallery was carved into the rock, leading from within the reduit to the Fort Obergrünewald ditch, ensuring there was a safe communication link with the town in the event of bombardment.
The Austrian gunpowder magazine had to be demolished in 1859/60 because it was on the planned route of the railway line to Ettelbruck. It was replaced by a new powder magazine under the ravelin.
Work began to dismantle the fort in 1872, with the demolition of the powder magazine. The reduit and the gorge wall were destroyed in 1874.