We've just got back from lewis, and there is a path around the perimiter, but it does cut through the avenue. It was fairly quiet, but there were people walking up throught the avenue and into the circle. There are also lots of notices about Margeret curtis guided walks (for about £20 I think) You can also visit their own exhibition, its along side the road towards Breasclete on the right. We got to meet Ron Curtis when we went, also their books are cheaper than the visitors centre and you get alot more info