In 950 AD, Duke Liudolf of Swabia, son of the current Holy Roman Emperor Otto I, decided to establish a stud farm for his cavalry during the Hungarian invasions of Europe on a widened area of the Nesenbach river valley south of the old Roman castrum. The land and title of Duke of Swabia remained in Liudolf's hands until his rebellion was quashed by his father four years later. In 1089, Bruno of Calw built the precursor building to the Old Castle.