Suger, friend and confidant of the French Kings, Louis VI and Louis VII, decided in about 1137, to rebuild the great Church of Saint-Denis, attached to an abbey which was also a royal residence. He began with the West Front, reconstructing the original Carolingian façade with its single door. He designed the façade of Saint-Denis to be an echo of the Roman Arch of Constantine with its three-part division and three large portals to ease the problem of congestion. The rose window is the earliest-known example above the West portal in France. The façade combines both round arches and pointed arches of the Gothic style.
Why were nine large portals used in the construction of the Roman Arch of Constantine?