There are often pines on hilltops (thin soil, shallow rooted?)but as often as not they're in a circle, suggesting they were planted for effect relatively recently and had no predecessors.

It seems to me that if "signposts" are available it would be in the form of isolated yews. They have the known reverence and they have the age (some say that, since young ones can generate from dying ones, they can be effectively immortal).