The Abbey of St. Martin, established in 1124 in Laon in northern France, was one of the earliest foundations of the Premonstratensian Order. Along with Cuissy Abbey and Floreffe Abbey it counted as one of the primarii inter pares, or senior houses, of the order.
The Premonstratensian community was founded by Barthélemy of Jur, bishop of Laon, in co-operation with Saint Norbert of Xanten, who settled it with twelve canons from Prémontré Abbey. It took over the site of an earlier college of canons regular, established in the Carolingian period, which had fallen into decay.
It was dissolved in the French Revolution. The church of St. Martin in Laon, dating from mid to late 12th century, is still in use as a parish church. The former monastic buildings were converted into a hospital in 1810.
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.