The nave is flanked on either side by an arcade of four arches. The space above the arcades is the triforium; the triforium opens into the nave as a gallery of triple arches (hence the origin of the name).
The clerestory is the expanse of nave wall that extends from the triforium to the ceiling; it is pierced with windows which give light to the church.
The tripartite elevation of the nave—its vertical division into aisle, triforium and clerestory—is an innovation of Gothic design which maximizes the wall space available for light and stained glass.
The grandeur and brilliance of the rose window in the west wall of the church is seen to best advantage especially in the late afternoon. The stone tracery of the rose extends nearly eighteen feet across, almost filling the nave gable.
This is a «simple» rose, having but a single cycle of twelve petals. In the center of the rose is David, King of Israel, playing the harp. Radiating from King David are 12 angels each playing a different musical instrument.