The Round Tower (Runder Turm) of Andernach is a large defensive tower dating to the 15th century. It is Andernach's symbol and is one of the mightiest fortified towers of its time. It was built under the direction of the town council of Andernach in the period before 1440 (round lower section, first mention in the construction records) and from 1448 to 1453 (octagonal upper section) as a fortified watch tower within the town fortifications.
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.