One of the greatest architectural innovations of the Gothic era in the 12th to the 16th century was emergence of the Gothic cathedral, perhaps the most iconic of which is the Notre Dame cathedral in the heart of Paris. No one can walk into these buildings and not be awed by the expansive space, the majesty of the high ceilings graced by arched buttresses and the exquisite stained-glass windows recounting Biblical scenes.

What holds these immense stone buildings together and prevent them from collapsing under their own weight? The answer lies in the set of structural support stones known as the “flying buttress”. Attached to the external walls, these beautifully shaped arched stones connect to huge buttresses built away from the walls. To survive the centuries, the buttresses must be in a state of ‘pure compression’, i.e., compression everywhere and for all wind and snow loads. If there were any tension on these buttresses, they would fall apart because they are just stacked stones. The fact that most Gothic cathedrals have withstood the test of time is evidence of the ingenuity of the stone masons, builders and artisans of the Gothic era.