Adytum

Adytum (from ἄδυτον, inaccessible), the shrine or inner room of a sacred building; hence applied in later times to the penetralia of the Temple at Jerusalem, which were accessible to the priests alone, especially the sanctuary, or "holy place," and still more to the "holy of holies," or inmost chamber. Ecclesiastical writers also employ it metaphorically to denote the recesses of the heart or spiritual nature, and sometimes to designate the deeper mysteries of divine truth. See AGION.

⇒See also the International Standard Bible Encyclopedia.