The Gothic style is spikily linear and restlessly active, reflecting the exalted religious intensity during the Middle Ages. During its later phase, Gothic construction is characterized by lightness and soaring spaces. The system of flying buttresses allowed the reduction of wall surfaces by relieving them of part of their structural function. Great windows could be set into walls, admitting light through vast expanses of stained glass. One important element of Gothic architecture is the spiritual and mysterious quality of light, reflecting religious symbolism.
via Architectural Digest