The Crusader structures called the Knights' Halls or the Citadel of Acre originally served as the Knights Hospitaller Compound. They extend over an area of c. 8,300 square meters. Archeological remains from the Hellenistic Period (300-63 BC), from the Early Arab Period (638-1099 CE), to a large extent from the Crusader Period (1291-1104 CE) and primarily from the 13th century, were uncovered in the compound area.
It was in the 13th century that Acre was the capital of the Crusader Kingdom of Jerusalem. The destruction of the Crusader structures during the Mamluk Period (1291-1517) left its mark on the compound.
During the Late Ottoman Period (1750-1918 CE), the citadel was built as part of the city's defensive formation on the ruins of the Crusader fortress and during the British Mandate (1918-1948), activists of Jewish Zionist resistance movements were held prisoner there and it served as the main prison in the North of Israel. The archaeological excavation of the Crusader remains and the exposure of a multi-period complex depict Acre's two golden ages – the thirteenth century and the eighteenth & nineteenth centuries.
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.