I share this, it is the part of the extra story of Time Odyssey, where it is described that the Phoenix Cloth destroyed the continent of Mu (Atlantis).
The map seems to be only a representation of this place to locate where the characters are in the story and not something precise that's why even some locations that are mentioned as the river Lethe do not appear in this one, it is more like the map of the Sanctuary in the battle of the twelve temples that was only to give a location to the characters and not a precise representation of this place (something that only appeared until Next Dimension).
It is only a small dimensional space within a Temple, this does not qualify as a universe in any way.