When the choir of the Basilica of Saint-Denis near Paris was rebuilt under the direction of Abbot Suger, three structural elements — each already known separately — were united for the first time in a single system, and Gothic architecture was born.

These three elements are the pointed arch, the ribbed (cross) vault, and the large stained-glass window. The round arch of Romanesque architecture pushes its load both downward and strongly outward; for this reason Romanesque buildings were bound to thick walls with few windows. The pointed arch directs the load more steeply, more downward — the lateral thrust is reduced. The ribbed vault gathers the weight of the ceiling onto defined lines (the ribs) and from there onto points, rather than a continuous surface. The load now rests not on the whole wall but on specific supporting points.

The consequence is revolutionary: the wall need no longer be load-bearing. In Suger's choir, the wall surfaces between the piers thinned and gave way to broad stained-glass windows. For Suger this was theological — coloured light pouring in was the divine seeping into the material world (lux nova). But the architectural result is lasting: Saint-Denis is the first building in which structure is rearranged to let light in; the starting point of three centuries of cathedral architecture.