Alt-Eberstein castle was originally built in 1100 as the primary residence of the Counts of Eberstein, but by the end of the 16th century had been abandoned and much of the castle was torn down to provide materials for other structures. Presently it is a German national monument and a State Palace of Baden-Wuerttemberg.
A spur castle situated on a once-strategic mountain peak, the fortress was constructed as the seat of the Counts of Eberstein perhaps as early as 1100. The oldest part of the castle remaining intact are the ramparts. The first historical mention of the castle occurs in 1197 as Castrum Eberstein. In the second half of the 13th century, the Ebersteins began construction on Castle Neu-Eberstein and the older seat declined in prominence and ultimately fell into disrepair; by 1573, it was uninhabited and thereafter became a quarry used by both the Eberstein descendants and locals. Starting in the 1800s, efforts have been made to preserve the site (which now consists solely of elements of the curtain wall and keep) and it presently one of the State Palaces and Gardens of Baden-Wuerttemberg, housing a restaurant and garden open to tourists.
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.