This medieval monastic church comprising nave, monks' quire and Lady Chapel was started in 1094 by Ralph Flambard, later as bishop, to complete the building of Durham Cathedral. It has all styles of architecture from Norman to Tudor, 2 carved stone screens, 4 chantries and a peerless set of misericords. It is famous as the home of `The Miraculous Beam'. Above the Lady Chapel is a large room, formerly the grammar school and now a museum. In the baptistry is a memorial to the poet Shelley and his wife. There are guided tours to the tower.