Gandalf blew Galadriel's cover?!

I remember reading in the Return of the King, that a power dwelt in Lothlorien that Sauron could not overcome unless he himself were to go there. I assume that that power is Nenya on the hand of Galadriel. So the Three Rings had a power of 'holiness' or preservation. The opposite of Sauron which is to destroy.

I think that the reason the One Ring was not hidden in either Rivendell or Lothlorien is answered by Elrond, "they would become islands under siege". Islands under siege explains that all else would be cut off from them; the water, the air, and such. Eventually they would be without the elements and die.

My difficulty lies in Narya. If Vilya and Nenya both prove to be very powerful in protecting realms, what realm does Narya protect? It seems as if it is a traveling realm. Also, if the Three Rings magnify the powers of the users, wouldn't Gandalf's powers be magnified? Or was Narya simply given to Gandalf to be kept safe? Anthony