<P> Like most medieval buildings, the windows at Chartres suffered badly from the corrosive effects of atmospheric acids during the Industrial Revolution and subsequently . The majority of windows were cleaned and restored by the famous local workshop Atelier Lorin at the end of the 19th century but they continued to deteriorate . During World War II most of the stained glass was removed from the cathedral and stored in the surrounding countryside to protect it from damage . At the close of the war the windows were taken out of storage and reinstalled . Since then an ongoing programme of conservation has been underway and isothermal secondary glazing was gradually installed on the exterior to protect the windows from further damage . </P> <Table> <Tr> <Td> </Td> <Td> Wikimedia Commons has media related to Stained glass windows of Cathédrale Notre - Dame de Chartres . </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> Wikimedia Commons has media related to Stained glass windows of Cathédrale Notre - Dame de Chartres . </Td> </Tr> <P> The cathedral has three great façades, each equipped with three portals, opening into the nave from the west and into the transepts from north and south . In each façade the central portal is particularly large and was only used for special ceremonies, while the smaller side portals allowed everyday access for the different communities that used the cathedral </P>

What would have attracted most pilgrims to chartres cathedral