Château de Joux. Originally built from wood, the first structure here dated from the 11th century, with external stone fortifications and dungeons
added in the 12th century. After passing through numerous owners, it was finally annexed by Louis XIV for France in 1678. Substantially modernized
by Vauban between 1678 – 1693. Captured by Austria in 1814. It was transformed into a fort and included in the Maginot Line in 1879 to prevent
German invasion from Switzerland. It has served as a prison for successive French governments between the 17th and 19th centuries.
The fortress now houses a museum of armaments.