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. This chapel dates back to the 14th century, was reconstructed in the 16th century and was founded by Blanche d'Avaugour, the Lady of Kergroix. It contains a stairway giving access to the upper floors. On the exterior wall is a tomb thought to be the burial place of Bishop Guillaume VI Anger who died in 1404. His episcopacy commenced in 1385. Next is the Chapelle des Morts de la Guerre and then what was the Chapelle de Montfort which is no longer in use. We then reach the chevet and the apsidal chapel called La Chapelle Notre-Dame de la Cherche, also called the Chapelle de la Vierge , It was constructed in 1343 by Roland de Dinan and Clémence d'Avaugour replacing an 11th-century chapel. On the left-hand side of the chapel entrance, there is an alabaster statue of the Virgin Mary with child. The child holds a bird in his right hand. On the right-hand side of the entrance is another statue of the Virgin Mary in gilded wood. It dates to the 18th century. The windows in the chapel are of 19th-century vintage save for the central window, which is by the stained glass artist Hubert de Sainte-Marie. The chapel has two tombs set within its walls. On the north wall is the tomb of Guillaume Beschard, who was the bishop from 1379 to 1385, and on the south wall the tomb of Guy Eder, the bishop from 1428 to 1431. Facing the apsidal chapel is the tomb of Canon François de Boisgelin which dates to 1633.