Why is Chartres cathedral of such outstanding importance in the study of Gothic art and architecture?

... and metamorphosis of the Chartres type"2. Having no gallery, the elevation was in three tiers yet despite the weight of the great vault, the cathedral was to be luminous like no other church had been before, to make this possible the master-builder of Chartres abandoned the quadripartite elevation3 which abolished the need for alternating supports. The abandonment of the quadripartite elevation in Chartres clearly shows the integration of "aesthetic and structural considerations, more specifically, the influence of aesthetics of light upon the development pf architecture"4. There have been at least five cathedrals on the site. Most of the present crypt, which is the largest in France, remains from the third reconstruction of the cathedral in 1020. The north tower was started shortly after 1134 and when it was nearly complete the south tower was begun. The sculpture of the Royal Portal was also installed and between the towers a small ...  more