In 1204, the conquest of Normandy by King of France Philip Augustus was the occasion of a disaster. One of his allies, the Duke of Brittany Guy de Thouars, laid siege to the Mont: being without success, he set fire to the northern part of the abbey. The losses suffered by the monks during this fire were subsequently compensated by the king. Thanks to this large donation, they began the construction of a 35-metre high building, the ‘Merveille’ (Wonder), which has three levels supported by sixteen powerful buttresses. An undeniable masterpiece of medieval Gothic art.