Plains are symbols of space and of the boundless Earth, but always in the horizontal as opposed to the vertical sense. When transposed to Heaven, the word denotes the boundless immensity in which the sky-gods dwell and to which psychopomps (conductors of souls) lead souls at death. Mithras was often called 'Lord of the Plains'.
In the Celtic world-view the plain was a specific designation of the Otherworld - Mag Meld, 'Plain of Joy'.
The word was, however, often transferred or applied to that other Earthly Paradise, Ireland itself, one of its names being Mag Fal 'Plain of Fal', Fal being itself a metaphor for kingship. One personification of the ‘plain’ was the goddess Macha (magnosia-Macha), who gave her name to the former capital of Ulster, Emain Macha. She thus symbolizes the kingship of the warrior. Plains seem to have been the ideal places for mortals to inhabit, mountains, by contrast, being the preserve of the gods. One of the tasks imposed upon a deity in exchange for services rendered or in fulfilment of some oath sometimes took the form of reclaiming one or several plains. This, for example, was the task imposed upon the god Midir by King Eochaid Airem, who had defeated him in a game of chess, a task which the god performed with ill grace. When the same task was imposed upon the goddess Tailtiu, she performed it successfully, but died of exhaustion. The plain was named in her memory and because that was where the shamrock first grew, the plant became the emblem of Ireland. Meldi, the Gaulish name for the modern French city of Meaux, may have been called 'pleasant' in the context of religious notions comparable with the Irish Mag Meld.
The Plain of Joy was also the Land of Youth, an Elysium where centuries passed in minutes, where the inhabitants never grew old and where the fields were covered in flowers which never died. Similar fields of Paradise, replete with every delight, were the Elysian Fields of Greco-Roman mythology and with them corresponded the Fields of Ialu of the Ancient Egyptians. The latter were also known as the Fields of reeds, of Food, or of Offerings, and to them went the dead who had passed the test of weighing the soul. There they spent a godlike life of pleasure contemplating the Cosmic Egg, or the Sun-god Ra in his egg preserving 'the primeval vibration which was at the origin of that of light and of the word'. An antithesis of Hell, fields are a symbol of Paradise to which the righteous attain after death.
