Old town Rouen. Rouen in northern France on the River Seine, is the capital of the Haute-Normandie region and the historic capital city of Normandy. Once one of the largest and most prosperous cities of medieval Europe it was the seat of the Exchequer of Normandy in the Middle Ages. It was one of the capitals of the Anglo-Norman dynasties, which ruled both England and large parts of modern France from the 11th to the 15th centuries. It was here that Joan of Arc was executed in 1431.