The serial property comprises eight fortified sites – Castle and ramparts of Carcassonne and the fortresses of Aguilar, Lastours, Montségur, Peyrepertuse, Puilaurens, Quéribus, and Termes – representing a core part of the Capetian defensive system established in the 13th–14th centuries following the Albigensian Crusade. Built on rugged rocky ridges in strategically significant locations, these fortifications formed the backbone of the newly created seneschalty of Carcassonne, asserting the authority of the seneschal over the former territories of independent feudal lineages. Together, they illustrate the political, military and territorial consolidation of the Capetian Crown in Languedoc through ostentatious architecture adapted to dramatic topography.