While the builder of the Aarberg Castle is unknown, the city itself was founded between 1220 and 1225 by count Ulrich III of Neuchâtel. The count had recently acquired the rulership over this region and needed a central location from which to rule. The island and the key bridge was a natural location for a town. The castle may have been built around the time of the founding of the city.
The city was besieged in 1339, 1382 and 1386 but not taken. In 1358 the Graf (or Count) Peter von Aarberg was in financial difficulties and began looking for someone to buy the city. After years of unsuccessful attempts, in 1377-79 he was able to sell the city and his rights as ruler to Bern. The Bernese bailiff took up residence in Aarberg Castle in 1379. In 1380, the old castle roof was replaced with a new shingle roof. In 1419 and again in 1477, the town and castle of Aarberg were nearly destroyed in a fire. Both the town and castle were rebuilt following the destructive fires.
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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.