sanctum_sanctorum
1. [ noun ] a place of inviolable privacy
Synonyms: sanctum
Examples:

"he withdrew to his sanctum sanctorum, where the children could never go"

Related terms: retreat
2. [ noun ] (Judaism) sanctuary comprised of the innermost chamber of the Tabernacle in the Temple of Jerusalem where the Ark of the Covenant was kept
Synonyms: holy_of_holies
Related terms: place_of_worship sanctuary Tabernacle Judaism