While the builder of the Aarberg Castle is unknown, the city itself was founded between 1220 and 1225 by count Ulrich III of Neuchâtel. The count had recently acquired the rulership over this region and needed a central location from which to rule. The island and the key bridge was a natural location for a town. The castle may have been built around the time of the founding of the city.
The city was besieged in 1339, 1382 and 1386 but not taken. In 1358 the Graf (or Count) Peter von Aarberg was in financial difficulties and began looking for someone to buy the city. After years of unsuccessful attempts, in 1377-79 he was able to sell the city and his rights as ruler to Bern. The Bernese bailiff took up residence in Aarberg Castle in 1379. In 1380, the old castle roof was replaced with a new shingle roof. In 1419 and again in 1477, the town and castle of Aarberg were nearly destroyed in a fire. Both the town and castle were rebuilt following the destructive fires.
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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.