A chapel dedicated to Saint Michael was probably built on the "Treurenberg" hill as early as the 9th century. In the 11th century, it was replaced by a Romanesque church. In 1047, Lambert II, Count of Leuven, and his wife Oda of Verdun, founded a chapter in this church, and organised the transportation to it of the relics of the martyr Saint Gudula, which were housed before then in Saint Gaugericus' Church on Saint-Géry Island. The patron saints of the church, Saint Michael and Saint Gudula, are also the patron saints of the City of Brussels.