Mudd’s Women: Kirk’s cabin is on this deck (apparently) and has a decent stretch of corridor adjoining it.
The full corridor is seen only before Spock and the traveling circus enter the turbolift; after the turbolift ride (and thus supposedly after they reach Deck 12), we only see Kirk's cabin (the standard set), with the mood set by a brief glimpse of some utility corner or another behind a grillework.
Actually you also get to see the cross-brace? for the hallway outside of Kirk's quarters twice. Once when Mudd and Co come in and a second time when the miners enter Kirk's quarters. That's enough information to construct the 8' wide hallway section in front of Kirk's quarters.
There is also "Journey To Babel" and Deck 11 where they found the body of the Tellarite. It could fit in the neck area, but it would be tight on the width.
In any case, is there anything in TOS that pins the room label with the deck number and/or place deck 12 in the neck?