the Collegiate Church of Notre-Dame in Mantes and in the dynamically sculptural facade of Laon Cathedral (which also, unusually, has a rose window in its eastern end as well as in it transept ends). These windows have large lights contained in tracery of a semicircular form, like overlapping petals. The window that is central to the well-known Gothic façade of Notre Dame, Paris, is of more distinctly Gothic appearance, with mullions in two bands radiating from a central roundel, each terminating in pointed arches. It was this window, completed about 1255, that set the pattern for many other rose window including those of the transepts at St Denis and the gigantic and complex window in the south transept at Notre Dame. At Chartres, the transepts roses follow the style of the original 12th-century rose, elaborating on the theme of contrasting forms. The south rose combines the wheel with circles and semicircles, while the north rose introduces square lights which, rotating around the centre, are all set at different angles, creating a kaleidoscopic effect of great energy. Further development From the building of Chartres the dimensions of the rose window began to increase with the development of more elaborate window styles associated with Gothic architecture. By the middle of the 13th century the rose had attained the greatest possible size – the entire width of the nave or transept, as seen in the transept roses at St Denis and Paris. In the facades of St Denis, Chartres, Mantes, Laon and Paris, the rose was put under a circular arch. The next important development in its use for the Gothic style was to put it under a pointed arch, as was done in the Notre-Dame de Reims (after 1241), in the transepts as well as in the later roses of the facade. This form probably stemmed from the now destroyed St Nicaise, also in Reims. The rose window was often placed above a row of vertical lights as the apex of the composition, the small corner "spandrels" between the rose and lower tier being filled by smaller lights of rose form, as in the transepts of St Denis and Notre Dame. The last step in evolution of the Gothic style was to set the rose into a tier of vertical lights, of staggered height and surmount it by a tapering pointed light so that it became the centre of a vast window