Stonehenge is perhaps the world’s most famous prehistoric monument. It was built in several stages: the first monument was an early henge monument, built about 5,000 years ago, and the unique stone circle was erected in the late Neolithic period about 2500 BC in the early Bronze Age <br />It sits on Salisbury Plain in Wiltshire, England, two miles west of Amesbury. It consists of an outer ring of vertical Sarsen standing stones, each around 13 feet (4.0 m) high, seven feet (2.1 m) wide, and weighing around 25 tons, topped by connecting horizontal lintel stones. <br /><br />Inside is a ring of smaller bluestones. Inside these are free-standing trilithons, two bulkier vertical Sarsens joined by one lintel. The whole monument, now in ruins, is oriented towards the sunrise on the summer solstice. 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 tumuli (burial mounds).