Теодорих Великий
The city was fortified around 500 CE by order of Theoderic the Great, king of the Ostrogoths, and in 722 it was enlarged by the Lombard king Liutprand. An ally of Frederick Barbarossa in his war against the Lombardy communes, it took part in the destruction of Tortona in 1115, obtaining certain privileges in exchange. Around 1300 Castelnuovo became part of the Duchy of Milan.