About 150 km west of London. in the English county of Wiltshire, lies the UNESCO World Heritage Site of the Stonehenge, Avebury and Associated Sites.
Composed mainly of chalk and clay excavated from the surrounding area, Silbury Hill
is 37 metres (120 ft) high and covers about 5 acres (2 ha). It is part of the complex of Neolithic monuments around Avebury, which includes the Avebury Ring and West Kennet Long Barrow, and is the tallest prehistoric human-made mound in Europe and one of the largest in the world; it is similar in size to some of the smaller Egyptian pyramids of the Giza Necropolis. Archaeologists calculate that Silbury Hill was built about 4750 years ago and that it took 18 million man-hours, or 500 men working 15 years to deposit and shape 248,000 cubic metres of earth and fill on top of a natural hill. Its purpose however, is still highly debated.
In walking distance from Silbury Hill, Avebury
is the site of an ancient monument consisting of a large henge, several stone circles, stone avenues and barrows, surrounding the village of Avebury in the English county of Wiltshire. It is one of the finest and largest Neolithic monuments in Europe, about 5,000 years old. Although older than the megalithic stages of Stonehenge 32 kilometres (20 mi) to the south, the two monuments are broadly contemporary overall.
Most of the surviving structure is composed of earthworks, known as the dykes, consisting of a massive ditch and external bank henge. Although the henge is not perfectly circular, it has a diameter of about 420 metres (460 yd). The only known comparable sites of similar date are only a quarter of the size of Avebury. The ditch alone was 21 metres (69 ft) wide and 11 metres (36 ft) deep, with a sample from its primary fill carbon dated to 3300 - 2630 BC. The excavation of the bank has demonstrated that it has been enlarged, presumably using material dug from the ditch, so it could be assumed that the construction of the ditch could have started at the earlier date, although speculation puts it nearer the later date.
Within the henge is a great outer circle. This is one of Europe's largest stone circles, with a diameter of 335 metres (1,099 ft). It was either contemporary with, or built around four or five centuries after the earthworks. There were originally 98 sarsen standing stones, some weighing in excess of 40 tons. The stones varied in height from 3.6 to 4.2 m, as exemplified at the north and south entrances. The fill from two of the stoneholes has been carbon dated to between 2900 and 2600 BC. Nearer the middle of the monument are two additional, separate stone circles. The northern inner ring is 98 metres (322 ft) in diameter, but only two of its four standing stones remain upright. A cove of three stones stood in the middle, its entrance facing northeast. The southern inner ring was 108 metres (354 ft) in diameter before its destruction in the eighteenth century. The remaining sections of its arc now lie beneath the village buildings. A single large monolith, 5.5 metres (18 ft) high, stood in the centre along with an alignment of smaller stones.
Source: Wikipedia Silbury Hill