The fell is 609 metres (1,998 ft) high and stands along the south-east shore of Wastwater, the deepest lake in England.

Geologically, Illgill Head and Whin Rigg are part of the Borrowdale Volcanic Group, typical for the southern-western area of the Lake District.

In marked contrast to the north-western slope, the opposite flank of the fell, which descends to Burnmoor Tarn and Miterdale, is much gentler and covered in heather and bracken.

North-west from the cairn the grassy plateau gradually tilts, until a few yards away it simply disappears over the brink.

A lakeside path along the south-eastern shore of Wastwater starts at Wasdale Head Hall and continues through the boulder field with exhilarating close-up views of the Screes.