Rambam - Hilchot Beit Habechirah 7:22 The Laws of God's Chosen House We continue moving indoors, focusing on the innermost Temple Space. The Sacred Sanctum -- or Holy of Holies itself. We are now reaching the climatic Tenth level; the penultimate zenith of Geographic Kedusha! Although included in the structural embrace of the larger Temple Building, Maimonides, quite fascinatingly, pointedly identify it as a proverbial structure onto itself. The fact that only the High Priest, (e.g., Cohen Gadol) can enter -- and that even he is severely restricted in doing so -- is the positive proof of this highest level of Holiness. Interestingly, by this line of logic there seems to an even more restricted area exceeding this sacred space, yet it is ultimately removed from the running! It goes without saying that this climax of sanctity is explicitly spelled out in scripture, and most certainly biblically ordained.