Amongst the many rude stone circles scattered over Great Britain, Stonehenge is unique, in the fact of having its sarsen stones carefully though roughly worked; and also in the introduction of the horseshoe within the circles, in the design or plan of the building. As in the present day, our churches, in their design, symbolise the Cross, so we may fairly infer that the horseshoe at Stonehenge had its own special meaning, as it still has in the East. Stonehenge is a prehistoric monument in Wiltshire, England, 2 miles (3 km) west of Amesbury. It consists of a ring of standing stones, with each standing stone around 13 feet (4.0 m) high, 7 feet (2.1 m) wide and weighing around 25 tons. The stones are set within earthworks in the middle of the most dense complex of Neolithic and Bronze Age monuments in England, including several hundred burial mounds. Archaeologists believe it was constructed from 3000 BC to 2000 BC. The surrounding circular earth bank and ditch, which constitute the earliest phase of the monument, have been dated to about 3100 BC. Radiocarbon dating suggests that the first bluestones were raised between 2400 and 2200 BC, although they may have been at the site as early as 3000 BC. One of the most famous landmarks in the UK, Stonehenge is regarded as a British cultural icon. It has been a legally protected Scheduled Ancient Monument since 1882 when legislation to protect historic monuments was first successfully introduced in Britain. The site and its surroundings were added to UNESCO's list of World Heritage Sites in 1986. Stonehenge is owned by the Crown and managed by English Heritage; the surrounding land is owned by the National Trust. Stonehenge could have been a burial ground from its earliest beginnings. Deposits containing human bone date from as early as 3000 BC, when the ditch and bank were first dug, and continued for at least another five hundred years. Mike Parker Pearson, leader of the Stonehenge Riverside Project based at Durrington Walls, noted that Stonehenge appears to have been associated with burial from the earliest period of its existence: Stonehenge was a place of burial from its beginning to its zenith in the mid third millennium B.C. The cremation burial dating to Stonehenge's sarsen stones phase is likely just one of many from this later period of the monument's use and demonstrates that it was still very much a domain of the dead.[10] Stonehenge evolved in several construction phases spanning at least 1500 years. There is evidence of large-scale construction on and around the monument that perhaps extends the landscape's time frame to 6500 years. Dating and understanding the various phases of activity is complicated by disturbance of the natural chalk by periglacial effects and animal burrowing, poor quality early excavation records, and a lack of accurate, scientifically verified dates. The modern phasing most generally agreed to by archaeologists is detailed below. Features mentioned in the text are numbered and shown on the plan, right.