We're told Stonehenge was built in several stages and the general plan was changed each time. Whoever built it was familiar with the architectural principle of entasis -- that is, put a slight convex curve on the surface area of a column so that it looks straight at a distance. This shows accuracy in finishing the stone.

In this photo there's a child's face to the right of the smaller standing stone which gives some idea of the size of these upright megaliths.

Because Stonehenge is a circular construction, the lintel stones above the uprights had to be cut on a curve from the solid rock. Under the lintel stones there are holes or "mortices" cut in the rock to fit the tenons standing up on top of the uprights. This prevented the lintels moving once they were in place. There were more mortice and tenon joints at the ends of the lintels holding the lintels together end to end.

Farmers are concerned with their land and use what's available to improve it. For thousands of years they have been taking the smaller stones away and breaking them up to use as road beds, and ploughing down the cursus banks and ditches as they grow crops on them. So if neolithic farmers didn't build these great stone and earth works, who did, and why?