The large flying buttresses demonstrate the genius of the 13th century architects. Their construction is an exceptional architectural feat in Gothic architecture, both for their height and their thinness. Usually, flying buttresses are in two wings, separated from each other by an intermediate point of support. Here, the flying buttresses have only one wing, launched above the cathedral’s sides. Their tops support the height of the cathedral walls. They have a dual function: to shore up the façade to prevent it from collapsing under the weight of the vault and to solve the problem of draining rainwater without running off the stone.