The structure of the Library varies but generally from the outside it is shown as an extremely large tree with several windows and ledges, a door in the centre. The interior is mainly wooden and through the door there is a large open room, bookcases all along the walls and a staircase leads up to a bedroom, more bookcases along the walls and a single bed, a window and a small balcony. The library is quite dim and dark, but, due to the large amount of windows, there is a light and airy atmosphere.
The library is the setting for many situations in the show and appears in almost every episode.
-The place where Twilight was sent to stay by Celestia when she was checking how things were going for the Summer Sun Celebration and the location of the party that Pinkie Pie held for her in Mare in the Moon.
-The place where Rainbow Dash followed her back after the incident with Nightmare Moon to question her knowledge of the evil pony and her plot to keep Equestria in eternal darkness in Elements of Harmony.
-The place that she escapes the hoard of ponies that want the extra ticket to the Grand Galloping Gala and the place where all her friends give up the ticket to remove the pressure they have placed on her and the location that they receive tickets to the Gala each so they can go to the Gala together in The Ticket Master
-The place where Twilight shows Pinkie Pie that Gilda may not be such a mean pony but Pinkie might just be jealous in Griffon the Brush Off
-The place where Twilight stays to study the Ursa Major and hides from The Great and Powerful Trixie because she doesn't want to show off and have her friends hate her in Boast Busters.
-The place where Applejack and Rarity go to, to escape the rain and have the eventful sleepover in Look Before You Sleep.
-The place everybody meets up to find they have been cursed by Zecora in Bridle Gossip.
-The place where Twilight and Spike argue, due to not cleaning the library in time for Princess Celestia's visit and on of the places infested by Parasprites in Swarm of the Century.
-The place where Twilight begins her check list for helping out during the end of winter in Winter Wrap Up.
-The place where she experiments on Pinkie Pie in Feeling Pinkie Keen
-The main location of the episode Owls Well That Ends Well.