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.