The Cathedral of Our Lady is Roman Catholic church, see of the Diocese of Tournai in Tournai, Belgium. It has been classified both as a Wallonia's major heritage since 1936 and as a World Heritage Site since 2000.
There was a diocese centered at Tournai from the late 6th century and this structure of local blue-gray stone occupies rising ground near the south bank of the Scheldt, which divides the city of Tournai into two roughly equal parts. Begun in the 12th century on even older foundations, the building combines the work of three design periods with striking effect, the heavy and severe character of the Romanesque nave contrasting remarkably with the Transitional work of the transept and the fully developed Gothic of the choir.
The nave belongs mostly to the first third of the 12th century. Prefiguring the Early Gothic style, it has a second-tier gallery between the ground-floor arcade and the triforium. Pilasters between the round-arched windows in the clerestory help support the 18th-century vaulting that replaced the original ceiling, which was of wood, and flat.
The transept is the most distinctive part of the building, with its cluster of five bell towers and apsidal (semicircular) ends. The Cathedral was damaged by a severe tornado on the 24 August 1999. Assessment of the damage revealed underlying structural problems and the Cathedral has been undergoing extensive repairs and archaeological investigation ever since. The Brunin Tower was stabilised in 2003. In recognition of the Tournai cathedral's cultural value, UNESCO designated the building a World Heritage Site in the year 2000.