Never realised or understood quite what the significance of these stones were until I checked out the site...
Henblas is now a tourist-type farm attraction with childrens play area, falconry displays et al. One of the attractions is a bone-shaking ride on a tractor-pulled trailer which loops around the farm and does a circle about this monument. We thought it was a natural occurence until seeing the photograph on this site. I don’t know if it’s worth the ( not inconsiderable ) entrance fee to see the stones alone, but the kids loved the farm though..!