Bayonne has been inhabited since roman times, when it was known as Lapurdum. Its medieval fortifications were improved by Louis XII, and Francois I, enabling the town to defend itself against a Spanish army in 1523.
Vauban visited Bayonne sometime in the 1670's, and planned more improvements to the fortifications, including the construction of additional demi-lunes and a large, quadrangular citadel to the north of the river Adour. The city itself, which lies to the south of the Adour and is bisected by the river Nive, was surrounded by a wall of 9 rather eccentric bastions.
The citadel was designed from scratch by Vauban, and is a large square work with four bastions. It saw action against the invading British forces at the end of the Peninsular War, when it was taken by General Hill after a determined defence by the French.
The fortifications of Petit Bayonne, the eastern half of the town, had four bastions and one gate, the Porte de Notre Dame. To the west, Grand Bayonne had five bastions and two gates, the Porte d'Espagne and the Porte de la Poterne. The first gate is unusual in that it enters the walls through a bastion, not through the courtine as is normally the case.
The size and shape of each bastion is very different, and there are varying lengths between them, which makes the fortifications seem less regular than some. This is probably due to the way Bayonne was fortified in several stages, with improvements added gradually.
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.