Avebury is a Neolithic henge monument containing three stone circles, around the village of Avebury in Wiltshire, in southwest England. One of the best known prehistoric sites in Britain, it contains the largest megalithic stone circle in the world. "Wikipedia"

I ask the questions why did they also build the very large ditches seen here along the stone circles?
And how did they move these huge stones from a quarry far away and then lift and set them in the ground?