In 1231, Abbot Odo Clement began work on the rebuilding of the Carolingian nave, which remained sandwiched incongruously between Suger's Gothic works to the east and west.
 Both the nave and the upper parts of Suger's choir were replaced in the Rayonnant Gothic style.
From the start it appears that Abbot Odo, with the approval of the Regent Blanche of Castile and her son, the young King Louis IX, planned for the new nave and its large crossing to have a much clearer focus as the French 'royal necropolis'.
That plan was fulfilled in 1264 when the bones of 16 former kings and queens were relocated to new tombs arranged around the crossing, eight Carolingian monarchs to the south and eight Capetians to the north.
These tombs, featuring lifelike carved recumbent effigies or gisants lying on raised bases, were badly damaged during the French revolution though all but two were subsequently restored by Viollet le Duc in 1860.

The dark Romanesque nave, with its thick walls and small window-openings, was rebuilt using the very latest techniques, in what is now known as Rayonnant Gothic.
This new style, which differed from Suger's earlier works as much as they had differed from their Romanesque precursors, reduced the wall area to an absolute minimum.
Solid masonry was replaced with vast window openings filled with brilliant stained glass (all destroyed in the Revolution) and interrupted only by the most slender of bar tracery—not only in the clerestory but also, perhaps for the first time, in the normally dark triforium level.
The upper facades of the two much-enlarged transepts were filled with two spectacular 12m-wide rose windows.

As with Suger's earlier rebuilding work, the identity of the architect or master mason remains unknown.
Although often attributed to Pierre de Montreuil, the only evidence for his involvement is an unrelated document of 1247 which refers to him as 'a mason from Saint-Denis'.
In 1231, Abbot Odo Clement began work on the rebuilding of the Carolingian nave, which remained sandwiched incongruously between Suger's Gothic works to the east and west.  Both the nave and the upper parts of Suger's choir were replaced in the Rayonnant Gothic style. From the start it appears that Abbot Odo, with the approval of the Regent Blanche of Castile and her son, the young King Louis IX, planned for the new nave and its large crossing to have a much clearer focus as the French 'royal necropolis'. That plan was fulfilled in 1264 when the bones of 16 former kings and queens were relocated to new tombs arranged around the crossing, eight Carolingian monarchs to the south and eight Capetians to the north. These tombs, featuring lifelike carved recumbent effigies or gisants lying on raised bases, were badly damaged during the French revolution though all but two were subsequently restored by Viollet le Duc in 1860.
The dark Romanesque nave, with its thick walls and small window-openings, was rebuilt using the very latest techniques, in what is now known as Rayonnant Gothic. This new style, which differed from Suger's earlier works as much as they had differed from their Romanesque precursors, reduced the wall area to an absolute minimum. Solid masonry was replaced with vast window openings filled with brilliant stained glass (all destroyed in the Revolution) and interrupted only by the most slender of bar tracery—not only in the clerestory but also, perhaps for the first time, in the normally dark triforium level. The upper facades of the two much-enlarged transepts were filled with two spectacular 12m-wide rose windows. 
As with Suger's earlier rebuilding work, the identity of the architect or master mason remains unknown. Although often attributed to Pierre de Montreuil, the only evidence for his involvement is an unrelated document of 1247 which refers to him as 'a mason from Saint-Denis'.
Basilica of Saint-Denis