Avebury ring, aerial photograph. The circles of standing stones and the henge (ditch) at Avebury date from about 2500 BC. The entire site encompasses some 28 acres and comprises a perimeter ditch and bank enclosing an outer circle of stones and two inner circles of stones. The ditch and bank are approximately 0.4 km in diameter. The ditch, though still clearly visible, is about a third of its original depth of 10m. Within the perimeter is a circle of Sarsen stones, which have survived best on the western (left) half. Within the outer circle of stone were two smaller stone circles, one to the north and one to the south of the site, now separated by a road. The ring in the southern half has survived best. The site is part of the Avebury World Heritage Site. Photographed in Avebury, Wiltshire, UK.