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
Ffynnon Beuno and Cae Gwyn Caves Ffynnon Beuno and Cae Gwyn Caves Ffynnon Beuno and Cae Gwyn Caves are two Scheduled Ancient Monuments which are also designated a Site of Special Scientific Interest (SSSI) in Denbighshire, Wales. Two caves, with entrances close to each other high on a valley side above the Vale of Clwyd. They were first excavated in 1883-5. Human tools have been found on the site dating back to around 36,000 BC, and a mammoth bone has been dated back to 16,000 BC. These very early discoveries were significant in providing one of the first direct associations between stone tools of paleolithic people