Stonehenge

Stonehenge is a prehistoric megalithic structure on Salisbury Plain in Wiltshire, England, two miles (3 km) west of Amesbury [1]. It consists of an outer ring of vertical sarsen standing stones, each around 13 feet (4.0 m) high, 7 feet (2.1 m) wide, and weighing around 25 tons, topped by horizontal lintels held with mortise and tenon joints [1]. Inside is a ring of smaller bluestones, and within these are free-standing trilithons—two vertical sarsens joined by a single lintel [1]. The monument, now ruinous, is aligned to the sunrise on the summer solstice and sunset on the winter solstice [1]. The stones sit within earthworks in the densest complex of Neolithic and Bronze Age monuments in England, including several hundred tumuli [1].