The earliest traces of human settlement on the Sulzbach castle hill have been dated to the Late Hallstatt or Early La Tène culture. The medieval settlement was built first in the 8th century or early 9th century. The partially stone-made castle was built there in the 9th or 10th century. In 1003 the castle was moved to the Nordgaugrafen family by Henry II. The medieval castle was rebuilt from 1618 to the Renaissance style. Today the original tower from c. 1100 exists.
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.