 The Black Cuillin , which are mainly composed of basalt and <unk> , include twelve <unk> and provide some of the most dramatic and challenging mountain terrain in Scotland . The ascent of <unk> a ' <unk> is one of the longest rock climbs in Britain and the <unk> <unk> is the only peak in Scotland that requires technical climbing skills to reach the summit . These hills make demands of the hill <unk> that exceed any others found in Scotland and a full traverse of the Cuillin ridge may take 15 – 20 hours . The Red Hills ( Gaelic : Am <unk> <unk> ) to the south are also known as the Red Cuillin . They are mainly composed of granite that has weathered into more rounded hills with many long <unk> slopes on their flanks . The highest point of these hills is <unk> , one of only two <unk> on Skye . 
