It is really hard to explain where it is.  Guardian Palace is like on another dimension, but also in another world, by magical means.  It's on another plane, where the guardians can travel between our world and theirs, but it is also in the same world as outs, except changed by magic.  So it's really hard to explain it.  It sort of like you are sitting in your room, but if you were to be in the Land of the Guardian or in Guardian Palace you might be actually in the Library or Heero's room.  So the world is somewhat paralle.

    The history of Guardian Palace is even more confusing.  According to what my Guardian's have told me, and what I have heard from my other friends' Guardians.  Guardian Palace didn't seem to always exist in Land of the Guardians.  It seems before, anyone or anything could be a guardian and that they had no control.  So there was no leader or anyone to keep order.  It was whoever was the most powerful and had the most powerful Guardianee, they were the leader.  So it was ruled by fear.  Then something happened.  I'm not sure what, but somehow an Guardian rose to power, but it (I don't know if it was a he or a she) didn't seem as power hungery.  It seemed to have been able to set order to the Land of Guardians, allowing the Guardian Palace to appear.  The Guardian Palace wasn't built as you might build a building, but build from some hidden magic.  So I'm not sure what it is.
    According to my Guardians, there is some controversis.  The Guardians at first were not sure about our world, since we believe so little in magic and to them seemed boring.

    So this is what I know, if your Guardian can tell you more and I don't know, just tell me at guardianpalace@yahoo.com