Caves of the Mendip Hills traverse from one cave to another through the underground rivers led to the development of cave diving; the first cave dive attempt in Britain took place at Swildon's Hole in 1934. The first successful cave dive in Britain was achieved the following year at Wookey Hole Caves, where the last sump is currently the deepest in Britain at . The cave complexes at St. Dunstan's Well Catchment, Thrupe Lane Swallet, Lamb Leer and Priddy Caves have been identified as geological Site of Special Scientific Interest. There are also caves within the Cheddar Complex SSSI. A selection of the better known
Woodham Walter Common SSSI gravel over London clay. it has a number of areas of oak and hornbeam woodland on former heathland. It also has two botanically rich valleys, each of which has a stream along it. Poors' Piece and Pheasanthouse Wood have ancient woodland. Uncommon ground plants are pill sedge, broad-leaved helleborine and lady-fern. There are common brimstone and speckled wood butterflies, nightingales, hawfinches, badgers. and dormice. There is access to Woodham Walter Common from Common Lane. Woodham Walter Common SSSI Woodham Walter Common SSSI is an 80 hectare biological Site of Special Scientific Interest (SSSI) in Danbury in Essex. The site includes