The transept is composed of three parts:

• The northern cross-brace construction whose entrance bears the name of a blind man, Mantilius, cured by St Eleutherius;

• The mullioned and transomed window surmounted by the Lantern Tower, supported by four enormous pillars and flanked by four steeples achieving an extraordinary disposition as a “Cross of Jerusalem”. Towards the nave, the Brunin and Lattice Towers have upper Gothic bays. The Brunin Tower is thought to have taken its name from the first occupant of the Chapter’s prison to which it gives access. The Lattice Tower would evoke either the preparation of the wine that was done at its base, or a long candle rolled on a winch and lit in honour of Our Lady. Towards the choir, the St John and Marie Towers, from the name of the cathedral’s big bell traditionally called Marie-Pontoise, are purely Romance. The centre of the mullioned and transomed window is occupied by the choir-wall, Renaissance masterpiece of Corneille de Vriendt, called Floris, decorated with biblical scenes crowned with the effigies of the Virgin, and of St Eleutherius and St Piat, Tournai evangelists. From the top of the tribune, the Gospel was sung to the faithful gathered in the nave before the priest’s sermon.

• The southern cross-brace construction which opens on to the door of the Capitol. It owes its name to the proximity of the first municipal house of Tournai, known as “Capitol”. From the gallery that has been overhanging the door since the 16th century, the ecclesiastical judge, called the “Official”, attended the punishments.