Make of it what you will, but I think this throws an interesting light on why Silbury Hill was built as tall and as flat-topped as it is.
The crop circle is irrelevant, but the view of Silbury Hill from it isn't.
Mimics the landscape in all respects, eh? Still doesn't tell us why though.
http://www.cropcircleconnector.com/2013/silburyhill/groundshots.html
Atb,
TE.