Canterlot is a region that was added to My Little Pony in the Canterlot Wedding update on April 15, 2013. It is unlocked once the player has reached level 20. Travel between Canterlot and Ponyville is achieved by tapping the Train Station at the top of the map.
Canterlot features its own collection of characters, separate from those who live in Ponyville.
The members of the Mane Six—Twilight Sparkle, Pinkie Pie, Rarity, Applejack, and Fluttershy—as well as Princesses Celestia and Luna all travel to Canterlot, and while there they stay in the Canterlot Inn.
Once you've reached level 20 (or updated the game and were past level 20) you'll get a message from Princess Celestia.
Pinkie Pie: Oh my gosh! On my gosh! we're here! We're here!
Rarity: Goodness! Canterlot looks absolutely fabulous!
Twilight Sparkle: Come on everypony! We've got work to do!
Rarity: And you've got a big brother to congratulate!
Shining Armor: Twily!
Shining Armor: I've missed you, kid! How was the train ride?
Twilight Sparkle: It was fun! ... But how could you not tell your little sister that you're getting married?!
Shining Armor: It's not my fault! Princess Celestia has requested increased security, just in case.
Shining Armor: So I'm counting on you and your friends to help with the preparations. Especially since you're my best Mare!
Twilight Sparkle: You want ME to be your best Mare?! I'd be honored!
Twilight Sparkle: But at the same time you're marrying somepony I don't even know!
Shining Armor: Twily, Princess Cadence is your old foalsitter!
Twilight Sparkle: Cadence? As in THE Cadence? As in the greatest foalsitter in all the history of foalsitters?!
Twilight Sparkle: Cadence is only the most amazing pony ever! She's beautiful, she's caring, she's kind ...
Twilight Sparkle: I'll do my best to make her wedding absolutely perfect!
Shining Armor: Thanks Twily! I have to focus on my duties as Captain of the Royal Guard.
Shining Armor: So I really appreciate the help from you and your friends!
Spike: We won't let you down, Shining Armor! Let's get going!
Introduction to Changelings
Battling Queen Chrysalis
Twilight Sparkle: STOP EVERYTHING!
Queen Chrysalis: (Disguised as Princess Cadance) Why are you doing this to me?! Why do you want to ruin my special day?!
Princess Cadance: Because it's not your special day! It's mine!
Queen Chrysalis: So you escaped my minions! But you're still too late.
(Queen Chrysalis transforms into her real self and laughs.)
Twilight Sparkle: She's a Changeling! She takes the form of somepony you love and gains power by feeding on your love for them!
Queen Chrysalis: Right you are! And as queen of the changelings I must feed my subjects! And Equestria has more love than anyplace I've ever encountered! Ever since I took the Princess' place, I've been feeding off Shining Armor's love for her. He's under my grasp, and my minions would devour all of Equestria! So every moment Shining Armor grows weaker, and so does his spell to protect Canterlot!
Princess Celestia: I can't stop her! She's too powerful!
Queen Chrysalis: Shining Armor's love for Cadance is even stronger than I thought! Consuming it has made me more powerful than Celestia!
Princess Celestia: The Elements of Harmony... You must get to them and use their power to defeat the Changeling Queen.
Queen Chrysalis: Mwahaha! You can run, but you can't hide! My minions will stop you and Equestria will be mine! (Summons changelings)
Twilight Sparkle: We'll show you!
(After this, you need to defeat all the Changelings with each type of Element shard.)
Queen Chrysalis: It's all over. You cannot defeat the Changelings! Bwahahaha!
Twilight Sparkle: That's what you think! But the Elements of Harmony have awakened Shining Armor from your spell!
Shining Armor: W-wh-what's going on? Why are all these Changelings here?! I don't think I have enough strength to repel the evil queen and her Changelings!
Princess Cadance: My love for you will give you strength.
Queen Chrysalis: What?! Nooo!! Noooooooooooo! (Disappears)
Twilight Sparkle: That's incredible! Thanks to the love that Princess Cadance and Shining Armor have for each other, they were able to defeat the evil Changeling Queen, Chrysalis!
Princess Celestia: Now we have a real wedding to get together!
Twilight Sparkle: Seriously, though, I get why the queen of the Changelings wanted to be with you... But how did you get someone as amazing as Cadance to marry you?
Shining Armor: I told her she wouldn't just be gaining a husband, she'd be getting a pretty good sister... too!
Princess Cadance: The best little sister in the world!
Twilight Sparkle: Aw shucks... Now it's time for us to finish the wedding preparations!
Spike: We'll give it our all, Princess! It'll be the best wedding ever!
(After completing the quest "Taking the Cake")
Princess Celestia: Mares and gentlecolts, we are gathered here today to celebrate the union of the real Princess Cadance -- and Shining Armor. The strength of their commitment is clear. The power of their love, undeniable. May we have the rings please?
Spike: Coming up!
Princess Celestia: I now pronounce you mare and colt! This is your victory as much as it is theirs, Twilight. You persisted in the face of doubt, and your actions brought the real Princess Cadance back to us. Learning to trust your instincts is a valuable lesson to learn.
Pinkie Pie: Woo hoo! Then let's get this party started!
Shining Armor: Twilight! None of this would've been possible without you, little sis. Love ya, Twily.
Twilight Sparkle: Love you too, BBBFF. Now THIS is a great wedding!
Spike: Oh yeah? Just wait until you see what I have planned for the bachelor party!