Holy of Holies
The innermost room of the Tabernacle and of the Temple of Jerusalem.
The expression is a Hebrew idiom meaning "the most holy" thing or place.
In the Tabernacle this inner room measured 10 X 10 cubits (about 15 X 15 feet) and was separated from the outer room, or holy place, by means of a veil, or portiere, of rich woven fabric, hanging from four pillars overlaid with gold and standing on sockets of silver.
In Solomon's, Zorobabel's, and Herod's temples, the holy of holies was 20 cubits square and 20 high.
No windows admitted light into it; it was entered into, at least in the first temple, by a double folding door of olive wood with cherubim carved upon it.
Whether that door remained closed or open, a veil (2 Par 3) maintained the separation of the two places.
In the middle of the holy of holies of Solomon's temple stood the Ark of the Covenant, overshadowed by the wings of the two colossal cherubim.
As the Ark disappeared at the time of the ruin of that temple (586 B.C.), the holy of holies of Zorobabel's and Herod's temples contained nothing.
The high priest entered into this inner recess only once a year, on the Day of Atonement, to offer incense and the blood of the bullock and of the goat destined to atone for himself, his house, and the people.
New Catholic Dictionary