Books on radiocarbon dating
The henge ditch is 25m in diameter and sits at the end of the 1¾-mile avenue that leads from Stonehenge to the river.
Excavations in 2008 established that this outer henge was built around 2400 BC but arrowheads from the stone circle indicate that it is likely to be much earlier, dating to around 3000 BC.
Nine stone holes were identified, part of a circle of probably twenty-five standing stones.
History is set to be rewritten after an archaeology team led by the University of Birmingham and the Ludwig Boltzmann Institute for Archaeological Prospection and Virtual Archaeology in Austria discovered a major ceremonial monument less than one kilometre away from the iconic Stonehenge.Evidence for a second stone circle was found close to the River Avon, linked to Stonehenge itself by the Stonehenge Avenue.