Le Perthus became French territory after the Treaty of the Pyrenees (1659). The Spanish captured Bellegarde in 1674 and began work on new fortifications in 1675. These were not very far advanced when the place was recaptured by the French. In 1678 Vauban designed for Bellegarde a strong pentagonal fort with a detached hornwork extending southwards towards the frontier.
The defences consist of a five bastioned trace, with an upper tier and a lower tier. In front of the more vulnerable sections of wall, there is a ditch. There are three demi-lunes, again only on the more approachable sides of the fortress - on the east there is a sheer precipice.
During the War of the Pyrenees, the fortress was besieged in May - June 1793 by the Spanish and then by the French (in 1794).
During World War II, the fort was used as a holding prison by the Gestapo for escaped prisoners of war and enemy agents.
The fort is open to the public between June and September only and includes exhibits on the history of the fort, its archaeology and the surrounding area.
References:Sigmaringen Castle was first mentioned in the year 1077 in the chronicles of Petershausen monastery. The oldest parts of the castle are concealed beneath the alterations made during the 17th and the 19th centuries. The secret of the earliest settlement built on this defendable rock will never be fully revealed: large-scale excavation work would be necessary, which the extensive land development renders impossible. Judging from the many Roman remains unearthed in the area around Sigmaringen, the 12th century keep known as the 'Roman Tower' could be traced back to a Roman predecessor.
The castle remains that have been preserved (gate, great hall and keep) date back to the Staufer period around 1200. The castle remains were integrated into subsequent buildings. The foundations of the castle buildings are to a large extent identical to the surrounding castle wall.
These remains give us a good idea of how the castle might have looked during the 12th century.