It's man-made and you want to know if there's money involved. If you can put me in the area of a 50yard diameter maybe I can help you. Usually they're burial grounds but I can't tell by a picture alone. In the old days they even used it to light their candles there for their dead. Like today's votive stand. But, it could not be!!
Example:
It can also be measurements! It all depends on the grounds that you're stepping on! That's my opinion from my experience.
PS! If your rock is easily movable, forget all that I said. It does not apply.