Avebury was built during the Neolithic period and is the largest complex of Stone Circles & Avenues on earth. This site comprises an enormous circular earthwork, 400 m wide, with a deep external ditch whose circumference is over 1200 metres. Inside is a 400-metre diameter circle of immense standing stones, and inside that there are two more stone circles each 100 metres in diameter. From Avebury there run two stone avenues, each of which had about 100 megaliths. Altogether there were some 600 megaliths including those of the Sanctuary.