Castle of Friendship

The Friendship Rainbow Kingdom is a kingdom that is gained by Princess Twilight Sparkle in the My Little Pony Friendship is Magic  season four episode Twilight's Kingdom - Part 2. It includes at least a castle  in Ponyville.

Development
In a September 2013 presentation held by Hasbro Australia, a slideshow was shown depicting upcoming My Little Pony and Equestria Girls merchandise. One of the slides in the slideshow relating to Rainbow Power contains the text "QUEST FOR A KINGDOM".

Twilight's new home was designed by background designer Phil Caesar in conjunction with art director Ridd Sorensen and BG painter Geoff Manson. In May 2014, Jim Miller was asked regarding Twilight's new home "Any rooms we are yet to see? :) Involving a certain familiar-looking wooden library maybe?" and answered "You'll have to wait to find out!" Later in the same month, Miller was asked "So is there an official name for Twilight's new crystal-tree-house castle-thing?" and answered "You'll have to wait till season 5 to find out!"

History
In the chapter book My Little Pony: Twilight Sparkle and the Crystal Heart Spell, Twilight has her doubts about "being in charge of the well-being of a kingdom of ponies" and seeks out advice from others. She consults Princess Cadance and asks her friends for ideas for her "future kingdom".

At the beginning of My Little Pony Equestria Girls and its chapter book adaptation My Little Pony: Equestria Girls: Through the Mirror, Twilight worries that, now that she's a princess, Princess Celestia will expect her to lead a kingdom of her own, a possibility that Spike gets excited about.

On pages 12 and 13 of the story Reflections Part 1, Twilight worries that her responsibilities of being a princess will interfere with her magical studies. Rainbow Dash suggests she be "a magical wonder of the world and a princess with the responsibilities of an entire kingdom on her shoulders", noting that it "can't be that hard".

Twilight's Kingdom - Part 2
At the climax of the episode, the crystalline tree-castle is created from the mysterious chest that sprouted at the base of the Tree of Harmony in Princess Twilight Sparkle - Part 2. The chest is launched from the tree to a site on one side of Ponyville where, in a matter of seconds, the tree grows into its full size.

The tree-castle bears some resemblance to Golden Oak Library, at least the aboveground portion of which is destroyed earlier in the episode by Lord Tirek, but is many times larger and appears to have a multi-level castle in its branches, which includes a great balcony, two spires, and a tower. The structure has at least one banner flying on the side marked with Twilight Sparkle's cutie mark, and the top bears a large crystal star. Two sets of five strings of beads hang off the side of the structure much like the white beads that hang off the Tree of Harmony. At the foot is a great golden stair for the two-leaved golden door into the tree's body. Two open lancet windows flank the door.

The lobby's two stairs lead into the castle rooms where lancet two-toned green glass windows and crystalline lathed columns with scrolled tops line the hall decked by a brown rug with scrollwork. At its end is a golden-framed green glass fanlighted door to the throne room where the Mane Six and Spike each have a crystalline throne about a star-shaped dais on a golden dish on a violet rug with scrollwork. Even with its door are a set of green glass spire lights.

Season five
In an upcoming episode of season five, the castle reacts to the Mane Six's cutie marks, and a crystal platform rises from the center of the throne room and creates a three-dimensional interactive map of Equestria.

Depiction in the film
Twilight Sparkle and her friends are seen in this castle in the film, My Little Pony Equestria Girls: Rainbow Rocks, gathering books for the castle's library, when suddenly Twilight notices a book vibrating. The book has Princess Celestia's cutie mark on the cover. She opens it and finds out that her friends from Canterlot High School are in trouble. Through research, she discovers that three sirens were banished to the human world by Star Swirl the Bearded. She makes some adjustments to the Crystal Mirror from the first film to make it able to open at any time, as opposed to every thirty moons.

Merchandise
"MY LITTLE PONY fans can discover the newest royal empire inside the FRIENDSHIP RAINBOW KINGDOM castle playset, a grand three-level palace fit for a pony princess! Use the friendship keys to unlock a number of magical accessories within the kingdom, including a wardrobe, vanity, book, and treasure chest. Pony friends can travel the kingdom in style on the rolling cloud car, taking a ride down a fun swirly slide. Stops along the way include a lookout tower, golden balcony, swing, and more. Includes PRINCESS TWILIGHT SPARKLE figure, key, cloud car, and themed accessories. (Ages 3 years & up/Approx. Retail Price: $39.99/Available: Fall 14)". It includes depiction of Spike. The playset's packaging, displayed along with it by Hasbro at the 2014 American International Toy Fair, lists its name "FRIENDSHIP RAINBOW KINGDOM" with a trademark symbol. Some promotional photos are of a different version of the playset, in which the first floor's interiors are instead images of the same designs as in Canterlot Castle and the design of the second floor's interior is instead the same as of Golden Oak Library's first floor.

A Keys Of Friendship DVD cover depicts Princess Twilight Sparkle with the Friendship Rainbow Kingdom in the background.