Notre-Dame Cathedral in Tournai bears witness to a considerable exchange of influence between the architecture of the Île de France, the Rhineland and Normandy during the short period at the beginning of the 12th century that preceded the flowering of Gothic architecture. In the case of the nave and transept, the early date of the elevation to four levels and its subsequent widespread extension meets the criterion of considerable influence and is further reinforced in the transept by the masterly integration of a 'corridor triforium' and by the unusual composition of volumes. The early 12th-century construction in the nave of a 'viaduct' structure on a four-storey elevation is unique in a period where church builders limited themselves to three levels.

In its imposing dimensions, the cathedral is an outstanding example of the great edifices of the school of the north of the Seine, precursors of the vastness of the Gothic cathedrals. The nave and the transept meet the criterion of unique testimony, in the light of their outstanding state of conservation in a region that has lost virtually all its great basilicas of the Romanesque or pre-Chartres Gothic periods. This is particularly true of the sculpted decoration of the nave. Archaeological sources of exemplary value serve to put the environment of the cathedral into perspective.
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In recognition of the Tournai cathedral's cultural value, UNESCO designated the building a World Heritage Site in the year 2000.
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