Adytum

adytum: (Greek) the inner sanctuary of a temple, entered only by the priest.
agora: (Greek) public square or market place.
alternating supports: a system in which piers of complex section alternate with simple columns or pillars.

Adyton or Adytum - The inner sanctuary of a Greek temple whence oracles were delivered; also, more loosely, any private chamber or sanctuary.

See also: Church, Apex, Pilasters, Well, Trave