Harnham Hill is a north-facing chalk escarpment spanning around 2.8 to 3 hectares (7–9 acres) and offers a network of paths, including part of the Avon Valley Path that leads to the coast at Christchurch. The woodland habitat supports wildlife such as bats, butterflies, badgers, and birds. The land was gifted by Bishop John Wordsworth in 1898 so that “the people of Salisbury may freely enjoy it.” There is a memorial to Bishop Wordsworth along the top path of the slope - known as Bishop's Walk
At the western end lies the West Harnham Chalk Pit, designated as a Site of Special Scientific Interest (SSSI). This exposed chalk has mistakenly been said to produce lime mortar for Salisbury Cathedral in the 13th century. In fact, the chalk came from the pits either side of Old Blandford Road and behind Harnham Social Club. All the sites were closer to the cathedral. The remains of the pits can be said on the east side of Old Blandford Road and behind the Social Club. The West Harnham Chalk Pit has been described as "from the late Middle Ages" until its closure in 1976.
Archaeological finds from the Iron Age to Anglo-Saxon period reveal ancient human activity, most notably, Iron Age pottery. An Anglo-Saxon burial ground of 60 graves was discovered in 1846 and Neolithic to Bronze Age artefacts have been identified nearby.
The view from Harnham Hill has featured in paintings by John Constable (from circa 1811) and local artist Edwin Young (1831–1913).
The hill also appears in Thomas Hardy's Jude The Obscure.
Around 2017, efforts to improve and stabilise Bishop’s Walk were completed using local grants and volunteer help to create a safer, more accessible path