Arcadia is the
AD&D plane of
Lawful Lawful Good, between
Mechanus and
Mount Celestia. The landscape is one of orchards and farmland, and even the 'wild' areas conform to geometrical order in way which is subtly unnerving to someone from a
world shaped by
natural forces. The
Japanese deities dwell here, as do a variety of other good-but-strict powers, and especially the
Egyptian gods Isis,
Osiris and
Ra. The
Harmonium faction is strong here, and they stop people from exploring too much, or trying to find out how many layers the plane has.
See also:
Planescape,
Outer Planes.