Notre-Dame de Paris
Construction

The chronicler Jean de Saint-Victor recorded in the Memorial Historiarum that the construction of Notre-Dame began between 24 March and 25 April 1163 with the laying of the cornerstone in the presence of King Louis VII and Pope Alexander III. Four phases of construction took place under bishops Maurice de Sully and Eudes de Sully (not related to Maurice), according to masters whose names have been lost. Analysis of vault stones that fell in the 2019 fire shows that they were quarried in Vexin, a county northwest of Paris, and presumably brought up the Seine by ferry.

The first phase began with the construction of the choir and its two ambulatories. According to Robert of Torigni, the choir was completed in 1177 and the high altar consecrated on 19 May 1182 by Cardinal Henri de Château-Marçay, the Papal legate in Paris, and Maurice de Sully. The second phase, from 1182 to 1190, concerned the construction of the four sections of the nave behind the choir and its aisles to the height of the clerestories. It began after the completion of the choir but ended before the final allotted section of the nave was finished. Beginning in 1190, the bases of the façade were put in place, and the first traverses were completed. Heraclius of Caesarea called for the Third Crusade in 1185 from the still-incomplete cathedral.

Louis IX deposited the relics of the passion of Christ, which included the Crown of thorns, a nail from the Cross and a sliver of the Cross, which he had purchased at great expense from the Latin Emperor Baldwin II, in the cathedral during the construction of the Sainte-Chapelle. An under-shirt, believed to have belonged to Louis, was added to the collection of relics at some time after his death.

Transepts were added at the choir, where the altar was located, in order to bring more light into the centre of the church. The use of simpler four-part rather than six-part rib vaults meant that the roofs were stronger and could be higher. After Bishop Maurice de Sully's death in 1196, his successor, Eudes de Sully oversaw the completion of the transepts, and continued work on the nave, which was nearing completion at the time of his death in 1208. By this time, the western façade was already largely built, though it was not completed until around the mid-1240s. Between 1225 and 1250 the upper gallery of the nave was constructed, along with the two towers on the west façade.

Another significant change came in the mid-13th century, when the transepts were remodelled in the latest Rayonnant style; in the late 1240s Jean de Chelles added a gabled portal to the north transept topped by a spectacular rose window. Shortly afterward (from 1258) Pierre de Montreuil executed a similar scheme on the southern transept. Both these transept portals were richly embellished with sculpture; the south portal depicts scenes from the lives of Saint Stephen and of various local saints, while the north portal featured the infancy of Christ and the story of Theophilus in the tympanum, with a highly influential statue of the Virgin and Child in the trumeau. Master builders Pierre de Chelles, Jean Ravy, Jean le Bouteiller, and Raymond du Temple succeeded de Chelles and de Montreuil and then each other in the construction of the cathedral. Ravy completed de Chelles's rood screen and chevet chapels, then began the 15-metre (49 ft) flying buttresses of the choir. Jean le Bouteiller, Ravy's nephew, succeeded him in 1344 and was himself replaced on his death in 1363 by his deputy, Raymond du Temple.

Philip the Fair opened the first Estates General in the cathedral in 1302.

An important innovation in the 13th century was the introduction of the flying buttress. Before the buttresses, all of the weight of the roof pressed outward and down to the walls, and the abutments supporting them. With the flying buttress, the weight was carried by the ribs of the vault entirely outside the structure to a series of counter-supports, which were topped with stone pinnacles which gave them greater weight. The buttresses meant that the walls could be higher and thinner, and could have larger windows. The date of the first buttresses is not known with precision beyond an installation date in the 13th century. Art historian Andrew Tallon, however, has argued, based on detailed laser scans of the entire structure, that the buttresses were part of the original design. According to Tallon, the scans indicate that "the upper part of the building has not moved one smidgen in 800 years," whereas if they were added later some movement from prior to their addition would be expected. Tallon thus concluded that flying buttresses were present from the outset. The first buttresses were replaced by larger and stronger ones in the 14th century; these had a reach of fifteen metres (50 ft) between the walls and counter-supports.

John of Jandun recognized the cathedral as one of Paris's three most important buildings in his 1323 Treatise on the Praises of Paris:

That most glorious church of the most glorious Virgin Mary, mother of God, deservedly shines out, like the sun among stars. And although some speakers, by their own free judgment, because able to see only a few things easily, may say that some other is more beautiful, I believe, however, respectfully, that, if they attend more diligently to the whole and the parts, they will quickly retract this opinion. Where indeed, I ask, would they find two towers of such magnificence and perfection, so high, so large, so strong, clothed round about with such multiple varieties of ornaments? Where, I ask, would they find such a multipartite arrangement of so many lateral vaults, above and below? Where, I ask, would they find such light-filled amenities as the many surrounding chapels? Furthermore, let them tell me in what church I may see such a large cross, of which one arm separates the choir from the nave. Finally, I would willingly learn where two such circles, situated opposite each other in a straight line, which on account of their appearance are given the name of the fourth vowel; among which smaller orbs and circles, with wondrous artifice, so that some arranged circularly, others angularly, surround windows ruddy with precious colours and beautiful with the most subtle figures of the pictures. In fact, I believe that this church offers the carefully discerning such cause for admiration that its inspection can scarcely sate the soul.
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