I wasn't expecting the photo to be that big to be honest, not sure why that happened!
I've heard the stones are very old, some say neolithic, which wouldn't surprise me, but I've also heard the current alignment may not be their original placings. Other than that, I'm afraid I'm an incomer to these parts, so don't knw much more.
I did crawl through the central stone (also called the crick stone I think) the first time I visited, but haven't since, as it just didn't feel appropriate, and the ground either side of the stone seemed a little eroded last time I visited, so I contented myself with lying on my belly in the grass and just taking in my surroundings. I haven't visisted the stone circle further down though would like to at some point. My husband has a broken back, so the walk down to the Men-an-tol is usually enough for him.