The Collegiate Church Saint Gertrude (Nivelles in Wallonia), consecrated by Wazon, bishop of Liège, in presence of Henry III, emperor of the Holy Roman Empire (1046), is one of the Mosan art's masterpiece.

The interior of the collegiate church impresses through its dimensions: 102 m long for the central nave, which makes this one of the largest Roman churches in the world. [1]

Claudine Ronnay-Docmans writes in the Patrimoine majeur de Wallonie that these dimensions of the interior recalls the splendour of the Ottonian liturgy, as people is able to know it for the abbey of Essen (Germany) [2]

The Westwork, (in german, Westbau) has been reconstruted. Its current form (voted by the population of Nivelles), is the result of a (very long) reconstruction (which was finished in 1984), following severe damage by bombing in 1940.