The ruins of Illens castle stand on a rock wall above a loop of the Saane river. The castle stands on the opposite side of the river from the fortified town of Arconciel. The two castles secured both sides of a crossing (either a ford or a bridge) over the river. The castle is first mentioned between 1150 and 1276.
In 1366, the notoriously violent Count Peter of Aarberg moved into the castle and remained there for a short while. The chamberlain of Charles the Bold, Guillaume de la Baume, expanded the castle and when he left in 1470, it was an elegant and comfortable palace. During the conflicts leading up to the Burgundian Wars, Fribourg and Bernese troops stormed and damaged the building on 3 January 1475.
In 1900, it was partly repaired and expanded and served a community of Trappist monks.
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.