Fort Thüngen (popularly known as "Dräi Eechelen" (Three Acorns) in Luxembourg due to the three acorns on top of the three towers) is part of the historic fortifications of Luxembourg City built in 1732. It is named after baron Adam Sigmund von Thüngen, the Austrian commander-in-chief of the fortress. A large part of the fort was destroyed in the 1870s, with only the three towers remaining, and reconstructed in the 1990s. Right behind the restored Fort Thüngen now stands the Grand Duke Jean Museum of Modern Art (MUDAM) by the famous architect Ieoh Ming Pei, that opened its doors in 2006. A fortress museum is currently being built inside the fort.