 The gable of the south transept has an ornate 15th-century window in the "flamboyant" style an addition which owed much to the generosity of Olivier de Clisson.The master altar is located in the centre of the transept and the choir area is surrounded by an ambulatory with 12th-century stylobates and columns which give access to various side chapels.On the "gospel" side or north side of the choir, the first side chapel is the Chapelle Saint-Giles.