The first medieval walls of Genoa date to the 9th century, in the Carolingian period. Under the threat of an attack by Frederick Barbarossa, between 1155 and 1158, it was decided to quickly erect new walls. The two impressive surviving gates belong to this effort: Porta dei Vacca, to the west, and Porta Soprana, to the east. The new walls protected a much larger area, about 55 hectares, compared to the 20 of the Carolingian walled city. But in reality these mighty walls, with doors, towers and hatches, were of limited use. Genoa was defended by its ships which dominated the seas. The walls were therefore in large part a symbol for the powerful and proud city with which Frederick Barbarossa would have to come to terms.