Appleby Fells is a Site of Special Scientific Interest in the Eden district of Cumbria, England, near Appleby-in-Westmorland. The area is approximately a triangle with a right angle in the North East at Cow Green Reservoir. It extends westwards to near Knock and southwards to near Helbeck. The area overlaps the North Pennines AONB. The fells rise steeply above the Eden Valley, the scarp slope being deeply dissected by streams. Natural England states that "the great importance of the area lies in its rich variety of habitats and associated plant and animal species" and that "geologically there are important exposures of the Great Whin Sill quartz dolerite". According to data from Natural England the condition of 93% of the SSSI is designated "Unfavourable Recovering" and less than 5% is "Fa