On the subject of how the ruins are laid out, why, oh why, does it have 2 circular patterns when dealing with a culture where EVERYTHING else is angled? Even their orbs are angles. Their written language consists of angled triangles.
WHY, then, does the overall structure of the ruins contain 2 perfect circular structures/platforms?.
It is literally the only instance we have of the guardians ever making anything even remotely round, or with smooth edges. While I dont think its important to activating additional obelisks, it might have something to do with the location of the other 2 ruins.
We already know that the moon rises over the small "landing pad" and sets over the large one when standing right in the center of the ruins... so they are probably symbols for the moon... which is round.