The ancient castle Castra Martis was built on a steep southern slope above the gorge of the Voynishka River at the end of the 3rd-beginning of the 4th century as part of the Danube Limes. It occupied a key position in guarding the important Roman road from Bononia to Singidunum (Belgrade).
In 408, the Huns under Uldin took control of the site during an attack on the Eastern Roman Empire, apparently by treachery. The fortification was reinforced under Justinian I, but was completely abandoned after the Gothic invasions in 586.
The fortress consisted of two parts: a small square fortification (quadriburgium) measuring 40x40 m, with powerful circuĀlar towers with a diameter of 12.5 m in the corners and a castle with the shape of an irregular quadrangle. It covered an area of 1.55 ha. The castle was accessible only from the south, where the gate was situated. Probably at the end of the 4th century, the protection of the gate was reinforced by the construction of another narrower wall.
Foundations of a Roman bath were discovered northwest.The quadriburgium is well-preserved and revealed in its entirety. Its fortress walls, built of stone and three-row brick girdĀers, are 2.2 m thick and 2 m tall, and the southeast tower rises to 16.3 m.
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.