Inhabited since the Neolithic Period, Carcassonne is located in the plain of the Aude between historic trade routes, linking the Atlantic to the Mediterranean Sea and the Massif Central to the Pyrénées.

Its citadel, known as the Cité de Carcassonne, is a medieval fortress dating back to the Gallo-Roman period and restored by the theorist and architect Eugène Viollet-le-Duc between 1853 and 1879.

Carcassonne became strategically identified when the Romans fortified the hilltop around 100 BC and eventually made it the colonia of Julia Carsaco, later Carcaso, later Carcasum (by the process of swapping consonants known as metathesis).

In Francia, the Arab and Berber Muslim forces invaded the region of Septimania in A.D. 719 and deposed the local Visigothic Kingdom in A.D. 720;[10][11] after the Frankish conquest of Narbonne in 759, the Muslim Arabs and Berbers were defeated by the Christian Franks and retreated to Andalusia after 40 years of occupation, and the Carolingian king Pepin the Short came up reinforced.

The origins of Carcassonne as a county probably lie in local representatives of the Visigoths, but the first count known by name is Bello of the time of Charlemagne.

Viscount Raymond-Roger de Trencavel was imprisoned while negotiating his city's surrender and died in mysterious circumstances three months later in his dungeon.

During the Hundred Years' War, Edward the Black Prince failed to take the city in 1355, although his troops destroyed the lower town.

[12] In 1659, the Treaty of the Pyrenees transferred the border province of Roussillon to France, and Carcassonne's military significance was reduced.

The fortified city consists essentially of a concentric design of two outer walls with 53 towers and barbicans to prevent attack by siege engines.

[16] One section is Roman and is notably different from the medieval walls, with the tell-tale red brick layers and the shallow pitch terracotta tile roofs.

Later in the year the architect Eugène Viollet-le-Duc, already at work restoring the Basilica of Saints Nazarius and Celsus, was commissioned to renovate the place.

The fortifications were consolidated here and there, but the chief attention was paid to restoring the roofing of the towers and the ramparts, where Viollet-le-Duc ordered the destruction of structures that had encroached against the walls, some of them of considerable age.

Viollet-le-Duc left copious notes and drawings upon his death in 1879 when his pupil Paul Boeswillwald and, later, the architect Nodet continued the rehabilitation of Carcassonne.

The Lac de la Cavayère has been created as a recreational lake; it is about five minutes from the city centre by automobile.

Carcassonne, along with the French Mediterranean coastline, can be subject to intense thunderstorms and torrential rains in late summer and early autumn.

The newer part (Ville Basse) of the city on the other side of the Aude river (which dates back to the Middle Ages, after the crusades) manufactures shoes, rubber and textiles.

A major part of its income comes from the tourism connected to the fortifications (Cité) and from boats cruising on the Canal du Midi.

[23] The Gare de Carcassonne railway station offers direct connections to Toulouse, Narbonne, Perpignan, Paris, Marseille, and several regional destinations.

It was at the finish in Carcassonne that Mark Cavendish tied the record for most Tour de France stage wins (34) held by Eddy Merckx.

In May 2018, as the project "Concentric, eccentric"[25] by French-Swiss artist Felice Varini, large yellow concentric circles were mounted on the monument as part of the 7th edition of "IN SITU, Heritage and contemporary art", a summer event in the Occitanie / Pyrenees-Mediterranean region focusing on the relationship between modern art and architectural heritage.