Over a 400-year time, Luxembourg Castle (Château de Luxembourg) was repeatedly attacked and rebuilt by the Spaniards, Austrians, French, and Dutch, successively, to become the strongest fortress in Europe after Gibraltar. One such reinforcement was undertaken by the French military engineer Sébastien Le Prestre de Vauban, who redesigned the city's defensive fortifications after having orchestrated its siege in 1684 in the service of Louis XIV.

The heart of the old town is the Fish Market ,around which stand several 17th- and 18th-century buildings, including the mansion housing the Luxembourg National Museum Um Bock, a 13th-century building and the city's oldest, is also located at the Fish Market. Among the city's other cultural institutions are the Jean-Pierre Pescatore Museum of fine arts and the History Museum of the City of Luxembourg .At the town of Hamm 4 miles (6 km) to the east is a World War II military cemetery with the graves of more than 5,000 U.S. soldiers, including those of Brigadier General Edward Betts and General George S. Patton, Jr.