First, I worked on this place nearly five years, so I'm quite acquainted with the theories about its origin.
For now, we assume it's a natural phenomenon. What we know for certain is that this area was under the sea about fifty million years ago (plus-minus ten million), because, when you walk around, you see all those tiny seashells and fossils in the sand and on the stones. Scientists still haven't agreed on how did the stones finally took these forms, because, as you've seen, it gives the impression of being man-made.
However, people who support the theories that it's man-made lack evidences. The circle on this photo is the only spot in the whole area (about 2 square km) that we certainly know is made by man, because it happened in the 80s and the person that arranged the stones in such a way is still alive. All other versions sound more like a science fiction story for retards, at least the ones I've heard.
I'm no geologist and I can't bring more solid arguments, but from being there all this time, I've come up with my own conclusions. Of course, we can't know for certain, not yet. It's a mystery and this is what is drawing thousands people to this place every year.
I hope I've answered your questions