knoll (nôl) A small rounded hill or mound; a hillock.
[Middle English knol, from Old English cnoll.]

"Local legend has it that Chanctonbury Ring was created by the Devil and that he can be summoned by running around the clump of trees seven times anti-clockwise. When he appears he will offer you a bowl of soup in exchange for your soul. The Ring is also rumoured to increase fertility in women who sleep underneath the trees for one night." (wiki)