 Châtellerault lies on the river Vienne, a few km downstream from its confluence with the Clain in Cenon-sur-Vienne.Châtellerault was an important stronghold on the northern march of Poitou, established by the Count of Poitiers to secure his borders in the early 10th century.The count's local representative, the Vicomte de Châtellerault was established as a hereditary appointment by the time of Airaud who was probably a kinsman of the counts of Auvergne and dukes of Aquitaine; his heirs were "vicomtes" (viscounts) until the mid-11th century.