In the 12th century, the abbey church of Saint-Denis was extensively redesigned by Abbot Suger. For the enlargement of the chevet (from 1140 to 1144), Suger first designed a new crypt which gave the elevated chevet a solid foundation. It then surrounded it with an ambulatory that opened onto juxtaposed radiant chapels, an innovation for the time. A great deal of space was given over to light and stained glass windows. Suger’s architect used a technique that was still in its infancy, the ribbed vault. Thanks to the buttresses built on the outside, the walls could be extended upwards and the openings multiplied. The Gothic style was born.