 Much of the existing landscaping on the south lawn was carried out by Bishop George Henry Law in the 1820s . This included the incorporation of the remains of the roofless great hall and the construction of a raised rampart around the inside of the wall accessible from one of the towers . Bishop Law also created a grotto which he used to display fossils from Banwell Caves which were also part of his estate . A range of tress and shrubs were planted including : a black walnut , Lebanon cedar , catalpa and ginkgo . In the 1830s , Bishop Law had a pool created next to the springs . This acts as a mirror on a still day providing reflections of the east end of the cathedral in the water . 
