 There are 167 windows, including rose windows, round oculi, and tall, pointed lancet windows.The architecture of the cathedral, with its innovative combination of rib vaults and flying buttresses, permitted the construction of much higher and thinner walls, particularly at the top clerestory level, allowing more and larger windows.Also, Chartres contains fewer plain or grisaille windows than later cathedrals, and more windows with densely stained glass panels, making the interior of Chartres darker but the colour of the light deeper and richer.