This wall is the outer wall of the center leg of the battery which contains protected magazines and storerooms. The square alcove straight ahead has a large ring in it that was used to tie onto and move the guns around. The purpose of the slot that goes down to ground level is unknown, then right next to that is a lantern alcove, and then there's another set of each type. The round circle in the right foreground is where a gun position was, now filled with concrete.
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