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
Leighfield Forest SSSI Leighfield Forest SSSI Leighfield Forest SSSI is an biological Site of Special Scientific Interest east of Skeffington in Leicestershire It consists of several fragments, including Tugby Wood, Loddington Reddish, Brown's Wood, Skeffington Wood and Tilton Wood, of the former medieval hunting Leighfield Forest, which straddles Leicestershire and Rutland. It is a Nature Conservation Review site, Grade II. These woods in the Eye Brook valley date back at least to the thirteenth century. The dominant trees are ash and oak. The diverse moths and beetles include some rare species, and others are at the northern limit of their distribution. There are