In plan it is a Latin cross, with a total length from east to west of about 105 m; the height of the nave vaulting is 23 m. The west front has a porch, added in the 14th century, and two unfinished towers, their upper portions dating from the 13th century; their decorations have been greatly mutilated.
The nave consists of eleven bays, including those of the west front, which, in the interior, forms a kind of transept, similar to some narthexes of English churches.
The windows of the aisles, the arches of the triforium gallery, and the windows of the clerestory use round-headed arches, but double pointed arches appear in the lower gallery and in the vaults of the nave and aisles.
The vaulting was originally sexpartite, but were rebuilt after a fire in 1293 in the prevailing quadripartite style.
The transepts have apsidal (semicircular) terminations.
Side chapels were added in the north aisle in the 14th century and in the south aisle in the 15th and the 16th centuries.
One of the latter (15th) is especially rich in decorations.
The flying buttresses of the building were restored in the 19th century in the style of the 12th century.
From the northwest corner of the nave runs the western gallery of a fine cloister erected in 1230; and next to the cloister is the chapter house of the same date, with its entrance adorned with statues of the bishops and other sculpture.

The main interior elevation is typical for a transitional Gothic church, with four stories: aisle arcade, gallery arcade, blind triforium and clerestory.
The overall elevation closely resembles that at Tournai Cathedral, with arches springing from columns.
This is altered in the transepts, where there is an aisle arcade, blind triforium, and lower and upper clerestories, and the line of the respond extends all the way to the floor.

Noyon's choir was rebuilt following an 1131 fire.
The arrangement of the apse, with its arc of columns, is similar to those of Saint Denis and Senlis Cathedral.
In plan it is a Latin cross, with a total length from east to west of about 105 m; the height of the nave vaulting is 23 m. The west front has a porch, added in the 14th century, and two unfinished towers, their upper portions dating from the 13th century; their decorations have been greatly mutilated. The nave consists of eleven bays, including those of the west front, which, in the interior, forms a kind of transept, similar to some narthexes of English churches. The windows of the aisles, the arches of the triforium gallery, and the windows of the clerestory use round-headed arches, but double pointed arches appear in the lower gallery and in the vaults of the nave and aisles. The vaulting was originally sexpartite, but were rebuilt after a fire in 1293 in the prevailing quadripartite style. The transepts have apsidal (semicircular) terminations. Side chapels were added in the north aisle in the 14th century and in the south aisle in the 15th and the 16th centuries. One of the latter (15th) is especially rich in decorations. The flying buttresses of the building were restored in the 19th century in the style of the 12th century. From the northwest corner of the nave runs the western gallery of a fine cloister erected in 1230; and next to the cloister is the chapter house of the same date, with its entrance adorned with statues of the bishops and other sculpture.
The main interior elevation is typical for a transitional Gothic church, with four stories: aisle arcade, gallery arcade, blind triforium and clerestory. The overall elevation closely resembles that at Tournai Cathedral, with arches springing from columns. This is altered in the transepts, where there is an aisle arcade, blind triforium, and lower and upper clerestories, and the line of the respond extends all the way to the floor.
Noyon's choir was rebuilt following an 1131 fire. The arrangement of the apse, with its arc of columns, is similar to those of Saint Denis and Senlis Cathedral.
Noyon Cathedral