A flying buttress is a graceful masonry support that projects from the side of a wall and adds strength to arches and piers that bear heavy loads. Notre Dame Cathedral in Paris is known for its flying buttresses, some of which can be seen on the exterior of the apse. The delicate cascade of the flying buttress belies its serious structural role. Without the flying buttress, Gothic cathedrals could not have reached the awesome heights they are known for.