You are starting to sound like Future Esthar! The only proof for the barrier being metalic plates is that when you go to Esthar you run into an entrance - a building that is slightly poping out of the holographic barrier (I would think the building should be solid, as you can climb into it) and it is the only place where you cee ripples in the field, not anywhere else, only where the entrance is (the ladder and the entrance).

You can't go in on the garden because you seem to be flying into a mountain, but the Raganrok can fly through the hologram.