Editing Basilica of Saint-Denis (section)

=== Chevet and transepts ===
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File:Basilique Saint-Denis - Abside, côté nord-est - Saint-Denis - Médiathèque de l'architecture et du patrimoine - APMH00002668.jpg|The apse, or east end of the cathedral, in 1878
File:Basilique Saint-Denis - Façade nord - Saint-Denis - Médiathèque de l'architecture et du patrimoine - APMH00003933.jpg|North transept (left) and north nave walls and buttresses (19th c.)
File:Saint-Denis Basilique Saint-Denis Südliches Querschiff 3.jpg|The Rayonnant south transept
File:Saint-Denis Basilique Saint-Denis Südliches Langhaus 3.jpg|South side of the nave, with buttresses and chapels
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The [[chevet]], at the east end of the cathedral, was one of the first parts of the structure rebuilt into the Gothic style. The work was commissioned by Abbot Suger in 1140 and completed in 1144. It was considerably modified under the young King Louis IX and his mother, Blanche of Castille, the Regent of the Kingdom, beginning in 1231. The apse was built much higher, along with the nave. Large [[flying buttress]]es were added to the chevet, to support the upper walls, and to make possible the enormous windows installed there. The masons used the same engineering concept that was used at the Abbey of [[Saint-Martin-des-Champs Priory|Saint-Martin-des-Champs]] to support the large chapel windows'''.'''<ref>{{Cite journal |last=Stanley |first=David J. |date=2006 |title=The Original Buttressing of Abbot Suger's Chevet at the Abbey of Saint-Denis |url=https://www.jstor.org/stable/25068292 |journal=Journal of the Society of Architectural Historians |volume=65 |issue=3 |pages=334–355 |doi=10.2307/25068292 |jstor=25068292 |issn=0037-9808}}</ref> At the same time, the transept was enlarged and given large rose windows in the new rayonnant style, divided into multiple lancet windows topped by trilobe windows and other geometric forms inscribed in circles. The walls of the nave on both sides were entirely filled with windows, each composed of four lancets topped by a rose, filling the entire space above the triforium. The upper walls, like the chevet, were supported by flying buttresses whose bases were placed between the chapels alongside the nave.{{sfn|Plagnieux|1998|p=15}}