and reached the apogee of its Roman development, with an amphitheatre and thermae of which foundations remain. In the 5th century, it became the seat of a bishopric and later a capital of Merovingian Neustria.

From their first incursion into the lower valley of the Seine in 841, the Normans overran Rouen. From 912, Rouen was the capital of the Duchy of Normandy