Caves of the Mendip Hills caves are listed below 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
Alyn Valley Woods and Alyn Gorge Caves 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 Valley Woods Special Area of Conservation and the southern part includes Loggerheads Country Park. The SSSI has an area of 190.3 hectares while the SAC covers 168.3 hectares. A large part of the site is covered by broadleaved woodland with sessile oak, ash and sycamore among the dominant tree species. Notable plants in the woods include stinking hellebore, green-flowered