Around 1076 Archbishop Gebhard of Salzburg, a follower of Pope Gregory VII in the Investiture Controversy, had the Petersberg fortress erected above the town in order to prevent Emperor Henry IV from crossing the Alps. The archbishop also had fierce enemies in the Carinthian ducal House of Sponheim, who after his deposition made several attempts to take possession of Friesach. Constant attacks by Duke Engelbert were finally repelled in 1124. In 1149 King Conrad III of Germany stayed at the castle on his way back from the Second Crusade, as did Richard the Lionheart returning from the Third Crusade in 1192, attempting to elude the guards of Duke Leopold V of Austria.
Today the castle is home to the Friesach City Museum, which features exhibits about the town's history, culture, mining industry and trade.
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.