Mendip Hills to the development of cave diving in Britain. The first cave dive was attempted at Swildon's Hole in 1934, and the first successful dive was achieved the following year at Wookey Hole Caves, which has the deepest sump in Britain at 76 m (250 ft). The cave complexes at St. Dunstan's Well Catchment, Lamb Leer, and Priddy Caves have been identified as Sites of Special Scientific Interest. The deepest cave in the Mendip Hills is Charterhouse Cave with a vertical range of . Many caves in the Mendip area were excavated for archaeological and natural history studies by pioneer explorer
Alyn Valley Woods and Alyn Gorge Caves helleborine and wayfaring tree. There are also areas of calcareous grassland with plants such as bloody cranesbill and lesser meadow-rue. Much of the site lies on an escarpment of Carboniferous limestone and there are three cave systems: Ogof Hesp Alyn, Ogof Hen Ffynhonnau and Ogof Nadolig. Lead ore, zinc ore, limestone and calcite were formerly mined in the area. Alyn Valley Woods and Alyn Gorge Caves Alyn Valley Woods and Alyn Gorge Caves is a Site of Special Scientific Interest on the border of Flintshire and Denbighshire in north Wales. Most of the site is also designated as the Alyn