One must imagine the city of Carcassonne, with this enclosure composed of high curtains with parapets and turrets, and, at intervals, high towers, dominating the country and commanding the neighbouring defences. Such she was at the end of the Empire and such she remained for several centuries. Occupied by the Visigoths, vainly besieged several times by Clovis and by the successors of that prince, she was not forced before the Eighth Century. At this date, she fell into the hands of the Arabs, with all of the surrounding country. The domination of the Mussulmans, however, was very ephemeral; occupied by them about 720, Carcassonne again became Christian thirty years later, in 759. Carcassonne became an important town. The city remains a fortress of the first order, almost impregnable, with its towers, its curtains and its vast _château_; but around it, on the slopes and at the base of the hill between the Aude and the city, extensive and flourishing boroughs are forming. These _bourgs_ are mentioned in 1067; more recent discoveries tell us that the two principal ones were Saint-Vincent and Saint-Michel. The latter was a commercial town inhabited by common people and workmen whose turbulent character caused great embarrassment to the viscounts during the Twelfth Century. From the beginning of that century, the notables of Carcassonne took the side of the enemy of their legitimate master, the Count of Barcelona, gave him their oath, and on two different occasions the Viscount, Bernard Aton, was chased by them from his capital. When he returned, in 1125, he took rigorous measures to assure his rule in the future. Each tower on the wall was confided to the care of a faithful noble who had to live in it with his family and his men, to do what was called _le service d’estage_. The feudal acts have preserved for us the name of several towers, the _turris monetaria vetus_, for example, but it would be difficult to state precisely to which of the existing towers the old names were given. To the same viscount, Bernard Aton, is attributed the construction of a great part of the present wall of the city, and almost the entire _château_; from the reign of the same prince dates also the old part of the church Saint-Nazaire. Let us begin with the _château_. An act of the year 1034 already mentions the residence of the Counts of Carcassonne, and the _sala_, in which the Bishop of Gerona, Pierre Roger, lived; it speaks of the kitchens, the chambers, the stables and the chapel Saint-Marcel. Later, the _castellum Carcassonne_ is always carefully distinguished from the citadel; the acts, in mentioning a _camera rotunda_, speak of the elm that ornamented the court and under which the feudal lords rendered justice, as Saint Louis did later at Vincennes. But these give very meagre information which the study of this building will happily permit us to complete.