Built by Matilda, William the Conqueror's wife, as a counterpart to her husband's Abbaye aux Hommes, the Abbaye aux Dames was founded in 1060 and consecrated in 1066 — the same year William invaded England. The abbey church, dedicated to the Holy Trinity, is a remarkable Romanesque structure that survived both the Hundred Years' War and the 1944 bombardment largely intact.
The building now serves as the headquarters of the Normandy regional council, so the interior can only be visited by guided tour. Tours are offered twice daily in English and French, and the access they provide — to the crypt, the chapter house, and Matilda's tomb — makes them very worthwhile. The surrounding quarter is quieter than the area around the castle and worth exploring on foot.