The library is a room located in Arendelle castle that contains a collection of books.
The knowledge contained in the library proved useful during Agdar's reign; following an incident in which Anna was injured by Elsa's magic, Agdar searched through the library shelves and found a book containing a map that provided directions to the Valley of the Living Rock, where he hoped Anna could be healed. Though Anna was restored to health, the accident led to her being separated from Elsa. During the thirteen year period of separation, Anna went to the library to help pass the time.
On the day of Elsa's coronation, the library provided the soon-to-be queen a place of solitude before the main ceremony; while she practiced concealing her powers for the ceremony, Elsa looked to a portrait of her father during his coronation in an attempt to ease her anxiety.
However, the library was not always a place of solace; during Elsa's winter, Hans trapped Anna inside the room to freeze to death. Though Olaf managed to find Anna and kept her warm by setting a fire, the room was slowly overtaken by ice forming from Elsa's magic, which threatened to trap the pair within.
The library is a spacious room lit by natural light coming from a window that overlooks the courtyard. The room contains tall bookcases lining the walls, as well as a table with a few ornaments. Above the table is a portrait depicting Agdar holding the orb and scepter at his coronation. There is also a grandfather clock in the room with a broad snowflake carving in the center of its pendulum. Beside the clock is another window with a bench seat underneath it.
In the center of the room, there is a maroon-red carpet with a black border. A few chairs are on the carpet, as well as a small sofa and a table with a chess set. There is also a teal vase with purple flowers on one of the tables next to one of the chairs. The library also has a heat source in the form of a fireplace, with everything needed to light and maintain it sat along side. To the right of the rooms main entrance is a table in the corner with an armillary sphere sat upon it.
The clock that Anna puts her feet upon is removed from the library at some point during the castle's thirteen year closure.