I visited the Holestone today, taking my Dad along after earlier unsuccessful attempts to find it. It turns out there was no need for my guide: the route has been signposted with the brown monument signs showing the way. That got us onto the Holestone Road ok, but we still managed to drive past the site twice since the gorse was hiding the stone and the information sign can't been seen from the road. Keep an eye out for a silver metal farm gate into a field with what looks like a group of bushes in it - that's the mound of rock the stone sits on.
Visited this site the year before last, pretty impressive but hard to find!
Unsurprisingly its located just off the Holestone road just outside Doagh. On top of a stony outcrop surrounded by gorse bushes and not easy to spot. We finally found it after three visits and with directions from a local historian friend.
If visiting, don't wear shorts......
Local tourist board lists it as an attraction and states that it was used in the 1800s or there abouts for marriages...