Besançon's Vauban citadel has been listed as a UNESCO World Heritage Site. Louis XIV of France conquered the city for the first time in 1668, but the Treaty of Aix-la-Chapelle returned it to Spain within a matter of months. While it was in French hands, the famed military engineer Vauban visited the city and drew up plans for its fortification. The Spaniards built the main centre point of the city's defences, 'la Citadelle', siting it on Mont Saint-Étienne, which closes the neck of the oxbow that is the site of the original town. In their construction, the Spaniards followed Vauban's designs.
In 1674, French troops recaptured the city, which the Treaty of Nijmegen (1678) then awarded to France. As a result of control passing to France, Vauban returned to working on the citadel's fortifications, and those of the city. This process lasted until 1711, some 30 years, and the walls built then surround the city. Between the train station and the central city there is a complex moat system that now serves road traffic. Numerous forts, some of which date back to that time and that incorporate Vauban's designs elements sit on the six hills that surround the city: Fort de Trois Châtels, Fort Chaudanne, Fort du Petit Chaudanne, Fort Griffon, Fort des Justices, Fort de Beauregard and Fort de Brégille. The citadel itself has two dry moats, with an outer and inner court. In the evenings, the illuminated Citadelle stands above the city as a landmark and a testament to Vauban's genius as a military engineer.
The Citadel is built on top of a large syncline on a rectangular field crossed across its width by three successive bastions (enclosures, or fronts) behind which extend three plazas. The whole is surrounded by walls covered by circular paths and punctuated by watchtowers and sentry posts. The walls are up to 15 to 20 metres high with a thickness between 5 and 6 metres.
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.