St. Catherine's Abbey in Stralsund is one of the few Northern German monasteries, whose Gothic substance has almost survived in its entirety. It was built by the Dominicans in 1251 and used as orphanage and public school after the Reformation. Nowadays, it is home to the famous German Oceanographic Museum and the Museum of Cultural History, offering a comprehensive collection of artefacts of the region’s history and heritage.
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.