The Holy of Holies (Tiberian Hebrew: קֹדֶשׁ הַקֳּדָשִׁים Qṓḏeš HaQŏḏāšîm) is a term in the Hebrew Bible which refers to the inner sanctuary of the Tabernacle where God dwelt. This area is defined by the four pillars which held up the veil of the covering and under which the Ark of the Covenant was held off the floor by its two staves and 300 years later the Temple in Jerusalem where the Ark of the Covenant was kept during the First Temple, which could be entered only by the High Priest on Yom Kippur after sanctifying himself. The Ark is said to have contained the Ten Commandments, which were given by God to Moses on Mount Sinai. It is currently thought to be located under the Dome of the Rock.
The construction "Holy of Holies" is a literal translation of a Hebrew idiom which is intended to express a superlative. Examples of similar constructions are "servant of servants" (Gen 9:25), "Sabbath of sabbaths" (Ex 31:15), "God of gods" (Deut 10:17), "Vanity of vanities" (Eccl 1:2), "Song of songs" (Song of Songs 1:1), "king of kings" (Ezra 7:12), etc.
In The Church of Jesus Christ of Latter-day Saints (LDS Church), the Holy of Holies is a room in the Salt Lake Temple wherein the church's president—acting as the Presiding High Priest of the church—enters to act as High Priest of Israel in direct relationship with God, in accordance with the LDS interpretation of the Book of Exodus. Hence, this Holy of Holies in the temple is considered by adherents to be a modern cognate to the inner sanctuary of the Tabernacle and Temple in Jerusalem.
The Holy of Holies is a room adjoining the celestial room of the Salt Lake Temple. The room is described in the Encyclopedia of Mormonism: "Beyond its sliding doors are six steps to similar doors, symbolic of the veil that guarded the Holy of Holies in ancient times. The sanctuary is of circular design with a domed ceiling. The appointments include inlaid wood, gold leaf, stained glass, and unique lighting." The room includes a twelve-foot stained glass window, designed by the Tiffany Glass and Decorating Company, depicting the First Vision of Joseph Smith.