Aude is a department in the Languedoc-Roussillon, Le Sud de France, named after the river Aude. The local council also calls the department “Cathar Country”.
“In the 13th century, the region saw the development of Catharism, a dualistic Christian sect with similarities to Gnosticism. This religion was very quickly judged to be heretical by the Catholic Church. Faced with its growing strength in the counties of Carcassonne and Toulouse, Pope Innocent III in 1209 declared a crusade against the Albigensians. The barons of the north united to form an army under the command of Simon de Montfort. Whereas the count of Toulouse Raymond VI received absolution, the Count of Carcassonne confronted the army alone. The city of Carcassonne became the refuge of numerous Cathars.” (Source: Wikipedia).
Today, reminders of the Cathars are dotted around the region, such as the chateaux at Queribus and Lastours.