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
Salmonsbury Meadows SSSI provide good habitat for a wide range of species. The SSSI is managed by haymaking which is followed by grazing by cattle. Hay cut from the SSSI is spread in the restoration area to support the introduction of additional wildflowers. The Ancient Monument is protected by low intensity grazing. Salmonsbury Meadows SSSI Salmonsbury Meadows () is an biological and geological Site of Special Scientific Interest in Gloucestershire, notified in 1985. The site is listed in the 'Cotswold District' Local Plan 2001-2011 (on line) as a Key Wildlife Site (KWS). The site is owned and managed by the Gloucestershire Wildlife Trust,