The area surrounding Nafplio has been inhabited since ancient times, but few signs of this, aside from the walls of the Acronauplia, remain visible. Subsequently, Byzantines, Franks, Venetians, and Turks added to the fortifications. It became a place of considerable importance, and has continued so down to the present day. In the time of the Crusades it first emerges from obscurity. Nafplio was taken in 1212 by French Crusaders of the Principality of Achaea. It became part of the lordship of Argos and Nauplia, which in 1388 was sold to the Republic of Venice, who regarded it as one of their most important places in the Levant. During the subsequent 150 years, the lower city was expanded and fortified, and new fortifications added to Acronauplia.
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.