The city of Carcassonne occupies a rocky outcrop overlooking the river Aude. She is best known as a fortified medieval town, but the human presence on the site dates from the sixth century BC. J-C. with the implementation of a habitat and a Gallic active urban center in Roman times. The third century AD. Jc, it acquires a wall whose remains are still visible in the inner enclosure. It is on the west side of this primitive fortification that Trencavel viscounts built the castle in the twelfth century, enlarged and surrounded by a wall a century later. Following the crusades against the Albigensians, the Viscount is attached to the kingdom of France in 1226. The thirteenth century, the construction of the outer wall and the modernization of the inner rampart of the city are an impregnable fortress. From then until the signing in 1659 of the Treaty of the Pyrenees, Carcassonne becomes the main room of the defense of the border between France and Aragon. Saved from demolition thanks to the efforts of scholars Carcassonne and Prosper Merimee, the City will be between 1844 and 1911, a major restoration project by the French government entrusted to the architect Eugène Viollet-le Duke. Property of the Ministry of Culture, the castle and the ramparts of the city are open to the public by the Centre of National Monuments.