St Martin's Cathedral, also called St Martin's Church, is a church and former cathedral in the Belgian city of Ypres. It was a cathedral and the seat of the former diocese of Ypres from 1561 to 1801, and is still commonly referred to as such. At 102m tall, it is among the tallest buildings in Belgium.HistoryConstruction started on the church in 1230, and was finished in 1370. There had previously been a Romanesque church in the area, dating from the 10th or 11th century.The diocese was originally part of the Diocese of Thérouanne, which had been established in the 7th or 8th century. In 1553 Charles V besieged the city of Thérouanne, then a French enclave in the Holy Roman Empire, in revenge for a defeat by the French at Metz. After he captured the city he razed the city. In 1557, as a result of the war damage to its see, the diocese was abolished. This led to a reform of sees at the Council of Trent, Council of Trent, and the bishopric of Thérouanne was split between the Diocese of Saint-Omer, the diocese of Boulogne and the Diocese of Ypres. With this, Saint Martin's Church was elevated to cathedral status, as it became the see of the new diocese.