Caves of the Mendip Hills then rising up a fracture in the rock. Few caves on the Mendip Hills are more than deep or a few kilometres in length, (with some notable exceptions, such as Swildon's Hole which is over long), but a number are complex with several levels of passages which have been abandoned by the water, for example those around Cheddar. The catchment area of the Cheddar Yeo, which rises in Gough's Cave, measures . Dye marking shows that some of the water travels underground for up to , taking up to 14 days to reach Cheddar. When Banwell Bone Cave was discovered
Wookey Hole Caves plateau before sinking at the limestone boundary into cave systems such as Swildon's Hole, Eastwater Cavern and St Cuthbert's Swallet; the rest is rain that percolates directly through the limestone. The temperature in the caves is a constant . The caves have been used by humans for around 45,000 years, demonstrated by the discovery of tools from the Palaeolithic period, along with fossilised animal remains. Evidence of Stone and Iron Age occupation continued into Roman Britain. A corn-grinding mill operated on the resurgent waters of the River Axe as early as the Domesday survey of 1086. The waters of the