3.The Barriers or external fortifications
Beyond the ditch, at the end of the bridge, rose a fortification more or less considerable of which object was to protect the observation posts and the garrison exits. Sometimes it is composed of one or more towers, and even of a little castle, which was given the name "bastille".
More frecvently, especially in not very big castles it was used one or more enclosure of palisades.
A fortress placxed on a height with raps had sometimes a weeper which gave in plain and it was attached to the fortifications. It was like a long passage between two walls, sometimes flanked of the towers, and ending in a sort of separated fort. it sees such a disposition at the fortifications of the Carcassone town, in the post which looks to the modern town.