Golden Oak Library

Golden Oak Library was a large hollowed-out tree and the home of Twilight Sparkle, Spike, and Owlowiscious. The main reading room was on the ground floor, while the bedroom was on the second floor. There was also a basement where Twilight Sparkle performs her measurements on Pinkie Pie in Feeling Pinkie Keen. It is also called (the) Golden Oaks Library in some merchandise, and Twilight's Library in Gameloft's mobile game.

The tree had a large beehive hanging from a branch, a candlestick sign on the front door (sometimes an actual candlestick figure, depending on individual animation errors), a sign of an open book outside the door, and two balconies, one of which had a telescope.

According to Lauren Faust, Golden Oak Library was originally called "The Tree of Knowing".

The library is destroyed during the events of the season four finale but is subsequently replaced by the Friendship Rainbow Kingdom.

Season one
In Friendship is Magic, part 1, Princess Celestia sends Twilight to Ponyville to supervise the Summer Sun Celebration preparations. She was supposed to stay in the library during her stay in Ponyville. The library is protected from lightning by a magical lightning rod as mentioned by Twilight in Look Before You Sleep. During the thunderstorm, Twilight has a slumber party with Applejack and Rarity and during the end of the episode, a tree falls into the bedroom through the window. In Swarm of the Century, Twilight wakes up in the morning to find the library infested with parasprites. In Sonic Rainboom, Rainbow Dash crashes into the library and knocks all the books off the shelves, making Rarity, Twilight, Pinkie Pie and Applejack organize them again.

Season two
The library also has every Daring Do book in the series, as mentioned in Read it and Weep.

In times of difficulty, Twilight often turns to her vast library to find answers. For example, in The Cutie Pox, Twilight pulls out a book called Perplexing Pony Plagues to diagnose Apple Bloom's case of "Cutie Pox".

In Ponyville Confidential,  The Cutie Mark Crusaders attempt to find a way out of their current situation, after they try asking Rainbow Dash and Fluttershy, the trio go to the library in hope of getting help from Twilight Sparkle, Spike yells at them that Twilight anticpated their arrival, had set up a magic barrier.

Season three
In The Crystal Empire - Part 1, Twilight magically rips the entire tree out of the ground, exposing its roots. When Twilight and Spike are searching for a way to eradicate the Pinkie Pie clones in Too Many Pinkie Pies, Spike discovers a horseshoe-shaped button hidden in the back of a bookshelf. Upon pressing it, a secret compartment containing the desired book is revealed.

In Magic Duel, Trixie uses her magic to flip the library upside down and shake books from it to the ground to persuade Twilight to have a duel with her.

Season four
In Princess Twilight Sparkle - Part 1, Rarity mentions that after the Summer Sun Celebration, she and Twilight have a meeting schedule to redecorate Twilight's Loft now that she's a princess. As of Castle Mane-ia, it remained the home of Princess Twilight.

Her house also appears in Daring Don't, Power Ponies, Bats!, Pinkie Apple Pie, Three's A Crowd, Twilight Time, Maud Pie, Testing Testing 1, 2, 3, and Inspiration Manifestation.

In Twilight's Kingdom - Part 2, the library is destroyed by Lord Tirek. However, the library is later reborn into the Friendship Rainbow Kingdom.