Middos 4:2-3
Middos 4:2
The Great Gate had two smaller doors, one on the north and the other on the south. No one ever used the one on the south. This was the gate to which the prophet Ezekiel referred in Ezekiel 44:2: “Hashem said to me, ‘This gate must be shut; it may not be opened, nor may any person enter through it, because Hashem the God of Israel enters through it, therefore it must be shut.’” The kohein took the key and opened the (northern) small door and entered the chamber, and from there he entered the Heichal (the Sanctuary). Rabbi Yehuda says that the kohein used to walk in the thickness of the wall until he reached the place between the two gates. He then opened the outer doors from the inside and the inner doors from the outside.
Middos 4:3
There were 38 chambers there, 15 on the north, 15 on the south and eight on the west. In the north and south there were five chambers over five chambers, with another five chambers over these. On the west there were three chambers over three chambers, with another two chambers over these. Each chamber had three openings: to the chamber on its right, to the chamber on is left and to the chamber above it. The chamber in the northeast corner had five openings: to chamber on its right, to the chamber above it, one to the passageway, to the small door and to the Heichal.