Bishop Maurice de Sully launches the rebuilding campaign for a new cathedral on the Île de la Cité; later tradition associates the laying of the first stone with Pope Alexander III.
Work concentrates on the choir and its two ambulatories, establishing the eastern liturgical core that would allow services to begin before the full building was finished.
Medieval building history often notes the choir as substantially complete by this point (with some elements, such as vaults, treated separately in later work), marking a key milestone toward regular liturgical use.
Construction advances into the nave, with the first four bays, aisles, and galleries built—extending the processional space and increasing capacity for clergy and laity.
The high altar is consecrated, signaling functional completion of the choir and enabling full ceremonial use even as construction continued westward.
With major eastern work underway, builders begin the base of the west façade and continue the last nave bays, organizing the cathedral’s principal public entrance and monumental western elevation.
Work starts on the cathedral’s west façade, a long campaign that created the iconic three-portal front and the framework for the later twin towers.
The west front’s portals are built and sculpturally decorated, forming the primary didactic and ceremonial threshold into the cathedral.
A large west rose window is executed above the portals, expanding the façade’s glazing and reinforcing Gothic emphasis on light and vertical articulation.
The campaign continues with the upper parts of the façade and the two towers, alongside major upgrades: enlarged high windows, terraces, revised buttressing, and the addition of nave-side chapels.
Completion of the north tower marks a major milestone in the west front’s long construction sequence and the cathedral’s evolving skyline presence.
The south tower is finished, giving Notre-Dame its enduring twin-tower silhouette and enhancing its role as both landmark and bell-housing.
In a major Rayonnant modernization, Jean de Chelles lengthens the north transept, aiming for increased light and updated 13th-century stylistic coherence.
The north rose window is created as part of the Rayonnant transept program, intensifying the cathedral’s stained-glass emphasis and iconographic program.
The south transept is remodeled in the Rayonnant mode, including the creation of the south rose window (often dated to about 1260), further increasing glazed surface and interior illumination.
Work begins on new chapels around the chevet, expanding devotional and memorial space and reflecting growing elite patronage within the cathedral’s fabric.
Architect Pierre de Chelles is associated with major choir-area work (including elements such as the choir screen/rood screen program), advancing the 14th-century phase of reworking and embellishment.
The chevet chapel expansion is described as finishing by this point, completing a major reconfiguration of the cathedral’s eastern perimeter for additional altars and commemorative foundations.
Jean Ravy assumes responsibility for major continuing works, including finishing chevet chapels and initiating substantial structural and decorative efforts in the choir zone.
Under Jean Ravy, the choir’s flying buttresses are advanced, strengthening the high masonry while preserving the cathedral’s large-window aesthetic central to mature Gothic design.
After nearly two centuries of construction and 13th–14th-century redesigns, Notre-Dame’s medieval building campaign is commonly dated as completed by 1345, with later centuries bringing further alterations and restorations.
Notre-Dame de Paris: Construction and medieval modifications (1163–1345)
