It is open to the public from 9 a.m. to noon and from 2 p.m. to 7 p.m. in summer and from 9 a.m. to noon and from 2 p.m. to 5 p.m. in winter. Mass is celebrated here every Sunday at 11 a.m.
The first church is though to have been built in the 6th century during the reign of Theodoric, regent of the Visigoth kingdom. The church first appears in the official deeds in 925. On Thursday June 12, 1096, Pope Urbain II visited Carcassonne and blessed the stones used to build the cathedral of Saint Nazaire and Saint Celse. The construction was finished in the first half of the 12th century. Only the main and side naves of the Romanesque cathedral remain, which also featured a cloister. Part of the gothic transept and choir was built on the site of the Romanesque choir after 1269, when Louis IX granted the bishop and the chapter the right to encroach upon the public highway by a distance of two "cannes" (an old unit of measurement, representing about 3.5 metres). The gothic changes were finished in the 14th century under the bishoprics of Pierre de Rochefort (1300-1321) and Pierre Rodier (1323-1330). Numerous changes were made to the edifice that lost its cathedral status in 1803 to the Saint Michel church located inside the walled city. In 1898, Pope Leon XIII granted the title of basilica to the church. (Cl. M.H. 1840)

The main doorway, on a level with the third span in the north aisle, was probably built in the second decade of the 12th century. The door consists of 5 rows of coving supported, to each side, by five colonettes decorated with capitals. Only the two capitals nearest the door are original. Overall, the door was rebuilt by Viollet-le-Duc, based on the badly-worn features that have been stored in the Archaeology Museum (Musée Lapidaire).

The Romanesque nave has 6 spans. The ribbed vaulting on the barrel vaulted roof is supported on round or square pillars, as are the rounded arches in the side aisles. The shadowy nave was originally only lit by narrow windows in the walls of the side naves and occuli in the west wall. The decorations on the column capitals feature various motifs, including chequers, palmettes and interlacing. The nave comes together with the gothic transept, which replaced the Romanesque choir after 1270, in a movement of perfect architectural harmony. (Cl. M. H. 1840)
The transept and chancel in St. Nazarius' Cathedral were built on the site of the Romanesque chancel between 1269 and 1330. Each arm of the transept is 36 metres wide and consists of 3 rectangular spans leading into 3 flat-walled chapels. The chapels are lit by huge stained-glass windows, some of which date from the 14th century. Some of the large stained glass windows in the chapels date back to the 14th century.
The south rosace in Carcassonne cathedral's gothic transept features the coat of arms of Bishop Pierre de Rochefort (1300-1321). The colours are lighter than those in the north rosace, with shades that tend towards mauve. The central quatrefoil represents Christ in his majesty. The quatrefoils at the perimeter represent animals symbolising the four evangelists and the Church fathers. Peter can be recognised by the keys to heaven and earth, and Paul by his sword. These two saints are also represented in the chapel that houses the tomb of Pierre de Rochefort. (Cl. M. H. 1840)
The choir is illuminated by five stained glass windows. The central window depicting Christ is surrounded by two windows dating from the 16th century. The columns in the apse and the choir carried 22 statues representing the apostles, Christ, the Virgin and various saints. Many changes were made to the cathedral throughout the 17th century. Under the influence of Italian architecture, bishop Louis Joseph de Grignan (1679 - 1722) ordered the construction of a "Roman" choir with a marble altar surrounded by forged iron grills decorated with his coats of arms. (Cl. M. H. 1840)

The tomb of the bishop Guihèm Razouls or Radulphe (1255 - 1266) was discovered by Jean-Pierre Cros-Mayrevieille in 1839 in the chapel built by the prelate in 1260. On the west wall, an effigy in semi-relief of the bishop emerges from a niche. Dressed in all of his ornaments, the bishop can be seen holding his crook, without the volute, and raising his right hand in blessing. Beneath the frieze, three lines of text explain the death of the bishop and praise his charity. Sculptures on the lower part of the sarcophagus illustrate the ceremony of absolution, with twelve canons around the death bed, a bishop sprinkling the body and a woman praying. The sculptor added a touch of humour on the left-hand side of the monument in the shape of a hidden, laughing angel.
Bishop Pierre de Rochefort (1300- 1321) probably descended from a family of heretics from the "Montagne Noire". Under his bishopric, the south rosace was installed in the cathedral of Saint-Nazaire and the roof of the south transept was completed. His tomb is in the chapel between the nave and the north transept. The bishop is represented on the west wall, between the archdeacon of the diocese Pons de Castillon and the archdeacon Gasc de Rochefort. Three gables dominate the triptych. The bishop is blessing with his right hand and offering his crook to his followers. The plinth depicts the funeral procession with thirteen statuettes representing priests, canons and clerics. The ledger on the ground, which was restored in the 19th century, shows the coat of arms of the bishop, while angels praise on either side of the effigy of the deceased.

This low-relief fragment illustrating a siege is sealed in the west wall of the transept. The fragment dates from the first half of the 13th century. The attackers can be seen trying to enter a fortified town. Several theories exist about the representation of the siege stone, including the death of Simon de Montfort, who was slain by the city walls of Toulouse. The ledger located nearby is supposed to be part of the tomb of Simon de Montfort. Viollet-le-Duc and his successors questioned the authenticity of these archaeological remains.
The Chapel of the Virgin in the northern branch of the transept is illuminated by a stained glass window depicting The Jesse Tree, which represents an allegory of the family tree of Christian peoples through the ascendancy of Christ. The window is read from the bottom upwards and is made of 24 panels, each of which depicts a person. In the centre at the bottom, Jesse can be seen asleep. The genealogical tree emerging from his side represents the seven main ancestors of Jesus: his son, the king David, Solomon, Roboam, Abia, Asa, Josaphat and Joram. By each ancestor, the prophets look at the different generations as they rise towards the coming of the Messiah. In the spandrel of the window, Christ appears in his majesty, presiding over the resurrection, between the Virgin and the apostle John.
The window in the Sainte Croix chapel in the south transept represents the tree of life. This theme stems from the meditations of the Franciscan saint Bonnaventure (1221-1274) on the virtues and kindness of the Redeemer. The branches around the central trunk illustrate twelve virtues. Towards the top of the tree, Christ appears nailed to the red cross that is attached to the green trunk of the tree. The tree thus becomes the tree of the cross and the tree of eternal life. When the window was restored in 1853, Noah's Ark was added in the lower left-hand corner. The Ark of Alliance was added on the right-hand side, giving birth to the tree of Life of Original Sin. The Tree of Life was not born of paradise or of original sin, but of the crucifixion of Christ. The lower sections are assumed to represent the apostle John and the Virgin Mary.

Catholic reforms were introduced after the wars of religion. Bishop Vitalis de Lestang (1621- 1652) ordered Crespin Verniole to install an organ. The central part of the case remains, made by two cabinetmakers from Carcassonne: Jean Rigail and Jean Melair. The organ was rebuilt between 1680 and 1687 by Jean de Joyeuse, and was then enlarged between 1772 and 1775 by Jean-Pierre Cavaillé. Between 1900 and 1904, Michel Roger made changes to the instrument, leaving the wind chest and most of the pipes intact. The entire organ was restored between 1982 and 1985 by Barthélemy Formentelli using original parts and new pipes that were copied from the old organ. (Cl. M. H. 1840)
Claude Marquié – Le patrimoine des communes de la Méridienne Verte – Editions Flohic – 2000.
Site Officiel de l'Office de Tourisme et de la ville de Carcassonne - www.carcassonne.org
Site Officiel de l'Office de Tourisme et de la ville de Carcassonne - www.carcassonne.org