|According to ancient Celtic beliefs, three main realms co-exist: an Underworld associated with the past, an earthly realm of the middle world associated with manifested reality, and an Upperworld associated with potential reality and all possible futures where abstract concepts dwell with the divine.
The plains of the realms are divided into quarters by a vertical axis that interconnects and links them all together. This axis (Bilios) is one version of the world-tree, similar to the Germanic Yggdrasil or the Greek conception of an Omphalos. At the center all realms converge. Time flows like the waters of a river from the upper to the lower, and from east toward west. The southern realms are associated with the heat, energy and warmth of the summer half of the year, while the northern realms are associated with the static and cold of the winter half. The south and east are of the Deuoi, or Tuatha Dé Danann, while the north and west are realms of the Fomors.
This is why the myths depicted the gods arriving on the southeast coast of Ireland and the giants dwelling on Tory Island off the northwest coast. The divinities of Lír (ocean), the benevolent sea gods, dwelt in the southwest beyond the waves. The Tuatha Dé Danann were also associated with four realms; Falias (fail), "understone"; Gorias (gor), "warmth"; Findias (find), "white"; and Muirias (muir), "sea." Lia Fáil (lee-uh foyl or lee-uh faw-yil) means "the rock of the understone"; it is a divine analogue of the stone of truth??"a flat rock with footprints carved into it, which is stood upon when swearing oaths or delivering testimony.
This must stand for the manifested realm. Findias and Gorias may stand for the realms of atmosphere and fire, or the light of the sky. Muirias is certainly the waters surrounding the earth in the manifested world. The sea and other bodies of water were considered openings to the Underworld, a watery abode beneath this earth.
The three main realms:
The Upperworld called Nemos or Uindomagos (in Welsh, nef, or gwynfa; Irish, neamh or Magh Find/Magh Findargat)
The Middleworld, called Mediomagos (in Irish, Magh Mide)
The Lowerworld, called Andumnos or Antumnos (in Welsh, Annwn, or Annwfn; in Irish, Andomhain)
Even the geography of the countryside reflected Celtic conceptions of the magic of time and space. Ireland was divided into fifths, called coícit in Old Irish, now translated to mean "province." Four of these are still represented on maps of Ireland today:
Leinster (or Laigin) in the east
Munster (or Mumu) in the south
Connaught (or Connacht) in the west
Ulster (or Ulaid) in the north
Mide ("middle") was the central fifth, now remembered in County Meath and West Meath, which are now Leinster. The province of Mide or Meath was the ritual center where the tuathas/toutas of Ireland gathered annually and held festivals.