The Blackdown Hills are a range of hills along the Somerset-Devon border in south-western England, which were designated an Area of Outstanding Natural Beauty (AONB) in 1991. The plateau is dominated by hard chert bands of Upper Greensand with some remnants of chalk, and is cut through by river valleys. The hills support an extensive range of wildlife leading to the designation of 16 Sites of Special Scientific Interest (SSSIs). There is evidence of human occupation since the Iron Age.