The Holy of Holies is the most sanctified place in the Mikdash. It housed the Ark of the Covenant and the Two Tablets of the law. Only the High Priest was permitted to enter here, and only on Yom Kippur. In the center of the Holy of Holies stood the foundation stone upon which the Ark rested. Next to the Ark the jar of anointing oil was placed, as well as the container of Manna and Aaron's staff that had blossomed. The Holy of Holies was also called "Dvir" - because it was from the area between the two Cherubim that Moses heard G-d's word. 
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Contents:   Part I,    Part II,    Part III,    Part IV,    Part V,    Part VI,    Part VII