Larin Karr's Vault
The secret door in the north wall of the Hall of Hanged Men swings open to reveal a ten-foot-wide passageway extending to the north for some twenty feet into what should be inky darkness. However, periodically spaced everburning torches provide a source of light which reveals that after twenty feet of passageway, a room opens before you. And what a room it is! Bookcases line the walls from floor to ceiling, a large worktable occupies a fair portion of the center of the room, and two cushy easy chairs flank the worktable to the right and left. On the worktable is a large candelabra which holds four everburning torches which provide additional light. The knowledgeable wizards estimate that there are easily over 500 volumes in the library that extends before them.
The double lines on the map represent the bookcases. There are no doors leading out of this room. Also, the space to the south of the hallway into the library where the characters are shown to be on the map is the Room of Hanged Men.