I. INTRODUCTION Stonehenge, prehistoric monument on Salisbury Plain, in southwestern England, that dates from the late Stone and early Bronze ages (about 3000-1000 bc). The monument, now in ruins, consists of a circular group of large upright stones surrounded by a circular earthwork. Stonehenge is the best preserved and most celebrated of the megalithic monuments of Europe. It is not known for certain what purpose Stonehenge served, but many scholars believe the monument was used as a ceremonial or religious center. Stonehenge is not a single structure, but a series of structures that were rebuilt over a period of approximately 1,500 years. Little is known of Stonehenges architects. In the 17th century English antiquary John Aubrey proposed that Stonehenge was a temple built by Druids, a caste of Celtic priests encountered by the Romans as they conquered ancient Britain in the 1st century AD. Another early notion was that the Romans themselves constructed the monument. These theories were disproved in the 20th century, when archaeologists showed that work on Stonehenge began some 2,000 years before Celts, and later Romans, had arrived in the area. Today it is widely believed that Neolithic peoples of the British Isles began constructing the monument about 5,000 years ago.