Ratiaria, originally conquered by the Dacians and later by the Romans, was known for its gold mine possibly exploited by Thracians. The Romans became involved around 75 BC, and by 29 BC, Ratiaria was a fortified city. Under Augustus, the Romans officially conquered the region, organizing it into the province of Moesia. Ratiaria became a key station with a legionary fortress and fleet. After the division of Moesia in 86 AD, it became the capital of Upper Moesia.
Legio IV Flavia Felix was stationed here until the conquest of Dacia (101-106 AD). Afterward, Ratiaria became a colonia named Colonia Ulpia Traiana Ratiaria (107 AD). In the 2nd and 3rd centuries, it prospered as a trade center. With the definitive abandonment of Dacia Traiana in 271, old castra were reopened. By 285, Ratiaria served as the capital of Dacia Ripensis, hosting the military governor and the Roman legion XIII Gemina. It later became an important Christian center in the 4th century, with recorded bishops and theologians. The city faced sackings by the Huns in 440-441 and the Avars in AD 586. Archaeological excavations started in 1958, revealing its historical significance.
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.