Yarnbury Castle is the site of a multiphase, multivallate iron age hillfort near the village and civil parish of Steeple Langford, two miles along the A303 from Winterbourne Stoke, in Wiltshire. The site covers an area of 28.5 acres (11.5 ha), and has been extensively surveyed and investigated by the Royal Commission on the Historical Monuments of England (RCHME) in 1991, with finds of iron age and Romano-British pottery, iron age and Roman coins, and burials of human remains. There is much evidence of prolonged and extensive settlement of the site including for the evidence of around 130 separate structures of various sizes, most probably representing a mix of round houses, pits, and other features.