Mas de Las Fons castle was built from the 12th to 15th centuries. The Romanesque chapel dates from the 12th century.
From 1239, Raynaud, the Bishop of Quimper, decided on the building of a new chancel destined to replace that of the Romanesque era. He therefore started, in the far west, the construction of a great Gothic cathedral which would inspire cathedral reconstructions in the Ile de France and would in turn become a place of experimentation from where would later appear ideas adopted by the whole of lower Brittany. The date of 1239 marks the Bishop’s decision and does not imply an immediate start to construction. Observation of the pillar profiles, their bases, the canopies, the fitting of the ribbed vaults of the ambulatory or the alignment of the bays leads us to believe, however, that the construction was spread out over time.
The four circular pillars mark the start of the building site, but the four following adopt a lozenge-shaped layout which could indicate a change of project manager. The clumsiness of the vaulted archways of the north ambulatory, the start of the ribbed vaults at the height of the south ambulatory or the choice of the vaults descending in spoke-form from the semi-circle which allows the connection of the axis chapel to the choir – despite the manifest problems of alignment – conveys the hesitancy and diverse influences in the first phase of works which spread out until the start of the 14th century.
At the same time as this facade was built (to which were added the north and south gates) the building of the nave started in the east and would finish by 1460. The nave is made up of six bays with one at the level of the facade towers and flanked by double aisles – one wide and one narrow (split into side chapels) – in an extension of the choir arrangements.
The choir presents four right-hand bays with ambulatory and side chapels. It is extended towards the east of 3-sided chevet which opens onto a semi-circle composed of five chapels and an apsidal chapel of two bays and a flat chevet consecrated to Our Lady.
The three-level elevation with arches, triforium and galleries seems more uniform and expresses anglo-Norman influence in the thickness of the walls (Norman passageway at the gallery level) or the decorative style (heavy mouldings, decorative frieze under the triforium). This building site would have to have been overseen in one shot. Undoubtedly interrupted by the war of Succession (1341-1364) it draws to a close with the building of the lierne vaults (1410) and the fitting of stained-glass windows. Bishop Bertrand de Rosmadec and Duke Jean V, whose coat of arms would decorate these vaults, finished the chancel before starting on the building of the facade and the nave.
Isolated from its environment in the 19th century, the cathedral was – on the contrary – originally very linked to its surroundings. Its site and the orientation of the facade determined traffic flow in the town. Its positioning close to the south walls resulted in particuliarities such as the transfer of the side gates on to the north and south facades of the towers: the southern portal of Saint Catherine served the bishop’s gate and the hospital located on the left bank (the current Préfecture) and the north gate was the baptismal porch – a true parish porch with its benches and alcoves for the Apostles’ statues turned towards the town, completed by an ossuary (1514).
The west porch finds its natural place between the two towers. The entire aesthetic of these three gates springs from the Flamboyant era: trefoil, curly kale, finials, large gables which cut into the mouldings and balustrades. Pinnacles and recesses embellish the buttresses whilst an entire bestiary appears: monsters, dogs, mysterious figures, gargoyles, and with them a whole imaginary world promoting a religious and political programme. Even though most of the saints statues have disappeared an armorial survives which makes the doors of the cathedral one of the most beautiful heraldic pages imaginable: ducal ermine, the Montfort lion, Duchess Jeanne of France’s coat of arms side by side with the arms of the Cornouaille barons with their helmets and crests. One can imagine the impact of this sculpted decor with the colour and gilding which originally completed it.
At the start of the 16th century the construction of the spires was being prepared when building was interrupted, undoubtedly for financial reasons. Small conical roofs were therefore placed on top of the towers. The following centuries were essentially devoted to putting furnishings in place (funeral monuments, altars, statues, organs, pulpit). Note the fire which destroyed the spire of the transept cross in 1620 as well as the ransacking of the cathedral in 1793 when nearly all the furnishings disappeared in a « bonfire of the saints ».
The 19th century would therefore inherit an almost finished but mutilated building and would devote itself to its renovation according to the tastes and theories of the day.