Final Fantasy lll DS help getting past boulders in ancient ruins?

Right, so, I have gone into the ancient ruins. You know when you enter there are the three men, and then there is a path just below them where you go through? Well, I've gone through there and I think there were some boulders there before (I haven't played on this game in a while). So, after that, you keep going down, and there are two doors on your left. The one closest to you has a chest inside (which I've opened) the other door on the far left has like a long path where you go down stairs etc. Anyway, I followed the path, and I was just going to go down some more steps (btw after a while this path goes near water still inside the anicent ruins) when three boulders in a diagonal line were blocking my way from going down the stairs. Any help on how to get past these? Or is there something else I should do before going down here?