The classic story book castle always has a moat, but moats are only practicable on relatively flat land with a good water supply. In the Languedoc most castles - and especially the so-called Cathar Castles are built on hill tops, and are protected by sheer cliff faces.

These sheer cligff faces serve the same purpose as moats - namely to keep attackers at a distance and frustrate attempts at undermining. The castle shown here is Montsegur III, built on the site of Montsegur II, thye castle built as the Cathars' final defensive position.

A ravelin is a triangular fortification or detached outwork in front of the bastions of a fortress. Originally it was called a demi-lune. The ravelin is placed outside a castle opposite a fortification curtain. The edges of the ravelin are placed so that the guns there can sweep fire upon the troops that have to run along the fortification curtain. The wall facing the castle or fort is low and the angles of the others such that the ravelin provides no shelter to attacking forces if taken or abandoned by defenders.

Ravelines were introduced after the introduction of gunpowder and are typical of the seventeenth and eighteenth centuries.