Cathar castles (in French Châteaux cathares) is a moern term used by the tourism industry (following the example of Pays Cathare - Cathar Country) to arbitrarily designate the series of fortresses built by the French king on the southern frontier of his lands at the end of the Albigensian Crusade. Some of these sites had known, before the Royal period, fortified villages capable of sheltering Cathars and which were destroyed during the building of citadels.