The original Château de Coustaussa was built by the Trencavels, Viscounts of the Razès, in the 12th century. It was the stronghold of Cathars until Simon de Montfort and his Crusaders conquered it during the Albigensian Crusade. After the Crusades, the Castle came into the possession of the de Montesquieu family. The present Château was apparently still in good shape until the 19th century, when an enterprising local realised that he could turn a few Francs by stripping out and selling the woodwork.
References:The Château de Foix dominates the town of Foix. An important tourist site, it is known as a centre of the Cathars. Built on an older 7th-century fortification, the castle is known from 987. In 1002, it was mentioned in the will of Roger I, Count of Carcassonne, who bequeathed the fortress to his youngest child, Bernard. In effect, the family ruling over the region were installed here which allowed them to control access to the upper Ariège valley and to keep surveillance from this strategic point over the lower land, protected behind impregnable walls.
In 1034, the castle became capital of the County of Foix and played a decisive role in medieval military history. During the two following centuries, the castle was home to Counts with shining personalities who became the soul of the Occitan resistance during the crusade against the Albigensians.