Kullerstad church is a whitewashed Romanesque stone church dating from the 13th century. It is known of two Gunnar's bridge runestones: according runes there was a man named Håkon who dedicated a bridge to the memory of his son Gunnar. The first runestone was found in the exterior wall of the church of Kullerstad in 1969 and is raised in the cemetery. The second stone was discovered in a church only 500 metres away and is also raised in the cemetery. The second stone informs that Håkon raised more than one stone in memory of his son and that the son died vestr or 'in the West.'
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.