Caves of the Mendip Hills Caves of the Mendip Hills The caves of the Mendip Hills are formed by the particular geology of the Mendip Hills: large areas of limestone worn away by water makes it a national centre for caving. The hills conceal the largest underground river system in Britain. The hills consist of anticlines of Carboniferous Limestone lying over Devonian Old Red Sandstone, with the sandstone exposed on the summits. When a surface stream running off the sandstone reaches the limestone it sinks below ground through a "swallet", (also known locally as a "slocker"), continuing on its way down towards sea level by
Cheddar, Somerset the 2005 television programme "Seven Natural Wonders", Cheddar Gorge was named as the second greatest natural wonder in Britain, surpassed only by the Dan yr Ogof caves. There are several large and unique Sites of Special Scientific Interest (SSSI) around the village. Cheddar Reservoir is a near-circular artificial reservoir operated by Bristol Water. Dating from the 1930s, it has a capacity of 135 million gallons (614,000 cubic metres). The reservoir is supplied with water taken from the Cheddar Yeo, which rises in Gough's Cave in Cheddar Gorge and is a tributary of the River Axe. The inlet grate for the