History & CultureHow it works
How a Gothic cathedral gets walls made of glass.
A stone vault does not only push down, it pushes outwards. Romanesque churches absorbed that thrust with thick walls, which leaves almost no room for windows. Gothic builders instead set free-standing piers beside the building and spanned arches across. The thrust travels out along the arches, so the wall can be thin and full of openings.
Useful: When you see arches and piers on the outside, you know there is room for windows inside.
Source: en.wikipedia.org