Mendip Hills the hills. The western end of the hills is crossed by the M5 motorway and A38. Further east, and running almost north to south, are the A37 and A39. A wide range of outdoor sports and leisure activities take place in the Mendips, many based on the particular geology of the area. The hills are recognised as a national centre for caving and cave diving, as well as being popular with climbers, hillwalkers and natural historians. Wookey Hole Caves and some of the caves in Cheddar Gorge are open as show caves; however, many of the caves of the Mendip
Wookey Hole Caves system that is formed within the Dolomitic Conglomerate is characterised by shallow loops linking low bedding chambers, or tall narrow passages, known as 'rifts', developed by phreatic solutional enlargement of fractured rifts. The streamway in the inner part of the system formed within the limestone is characterised by deep phreatic loops reaching depths as much as , with the water flowing down-dip along bedding planes and rising up enlarged joints. In the far reaches of the cave the passages descend to below sea level. Witcombe suggests that the name "Wookey" is derived from the Celtic (Welsh) for 'cave', ""Ogo"" or