The Imperial Palace in Ingelheim was erected in the second half of the 8th century. Charlemagne chose Ingelheim in 787 as the location for his winter quarters, arriving there before Christmas and remaining there without interruption until the middle of 788. However the palace was not completed before completed before 814. It served Emperors and Kings as a residence and place for governance until the 11th century. From the buildings of the Imperial Palace impressive relics above ground are preserved today. The greater part of the complex remains as foundation under ground level and allows it to be the basis for archaeological excavations to reconstruct the entire system of buildings.
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.