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
Ham Hill, Somerset Ham Hill, Somerset Ham Hill is a geological Site of Special Scientific Interest (SSSI), Scheduled Ancient Monument, Iron Age hill fort, Roman site, Local Nature Reserve and country park, to the west of Yeovil in Somerset, England. The hill has given its name to the distinctive quarried hamstone and also to two nearby villages: Stoke-sub-Hamdon and Norton Sub Hamdon, whose names mean "under-Ham-hill" (where "Ham" is Old English for a small settlement). The Mendip Hills, Blackdown Hills, Quantock Hills and Dorset Downs are all visible from Ham Hill, especially from its war memorial. It is popular for picnicking, walking and