 To the north of the town are several caves of the Mendip Hills, including Thrupe Lane Swallet which is a geological Site of Special Scientific Interest (SSSI), and the St. Dunstan's Well Catchment which is an important cave system including a series of spectacularly-decorated caves which in total extend to about 4 miles (6.4 km) of mapped passage. The caves at Fairy Cave Quarry were formed mainly by the erosive action of water flowing beneath the water-table at considerable pressure (so called' phreatic 'development), but as the water table has fallen many of the caves now lie well above it and the system now contains a variety of cave formations (stalagmites, stalactites and calcite curtains) which in their extent and preservation are amongst the best in Britain. Shatter Cave and Withyhill Cave are generally considered to be amongst the finest decorated caves in Britain in terms of their sheer abundance of pure white and translucent calcite deposits. Small numbers of greater horseshoe bat (Rhinolophus ferrumequinum), lesser horseshoe bat (R. hipposideros) and Natterer's bat (Myotis nattereri) hibernate in the cave system. An area of nationally rare species-rich unimproved calcareous grassland of the Sheep's-fescue-Meadow Oat-grass type occurs in the field to the east of Stoke Lane Quarry.
