It is an unusual building: the towers are grafted on to the fourth bay of the nave instead of being part of the façade; there is a 20th-century portal in the façade, but the four original portals open into the aisles; and two secondary apses project to the south at 90° to the nave. It originally comprised two separate churches oriented at right angles to one another. The nave is very high and Rayonnant in style. The cathedral possesses a large expanse of stained glass windows, dating from the 14th through 20th centuries (those by Marc Chagall).