Atlantica

Atlantica is the central location for the popular Disney franchise The Little Mermaid. The kingdom is located beneath the Atlantic Ocean and is ruled by the sea king, King Triton. Atlantica's most famous resident is none other than King Triton's adventurous daughter Ariel and her best friend Flounder. These friends usually get Atlantica in hot water but cleans up the mess they sometimes start. The Kingdom was once ruled for a short time by the evil sea witch and former member of the royal court of King Triton, Ursula, who is now deceased.

Places of Interest

 * Triton's Palace: The home of King Triton, Ariel, Ariel's sisters and Sebastian. The palace holds bedrooms for every member, a large dining room, many hallways, a concert hall and a treasury.
 * The City: The area where the actual residents live in Atlantica. The city surrounds Triton's palace.
 * Ariel's Grotto: Ariel's former secret room, hidden in a cave. A large boulder hides the entrance. Ariel's grotto was once filled with many human items such as paintings, forks and spoons. It has held two separate collections of human items, all gathered by Ariel. Ariel was forced to destroy the first collection herself, after Ursula enchanted the objects to attack Atlantica. Ariel restarted her collection, but most of the items in the grotto were destroyed by King Triton in the film. However, at least twelve years later, the grotto had the collection in it again, either as a writers oversight, or implying that Triton repaired/replaced the items in the collection after the events of the original film.
 * Ursula's Lair: Around the outskirts of Atlantica. The home of Ursula and her eel henchman Flotsam and Jetsam. Here Ursula cast spells on merfolk and perform great pieces of magic. The lair itself is actually the remains of a giant deceased creature. The entrance houses many polyps, all who were previously merpeople whom hadn't been able to uphold their bargains with Ursula. The lair still stands today but its abandoned.
 * Ship Graveyard: An area filled with small sunken ships. Ariel and Flounder visit the graveyard often searching for human things.
 * Marketplace: Area where most people shop. In the animated series, Ariel travels here often with Urchin and Flounder.
 * Morgana's Lair: An area above and below where Morgana, Undertow, Cloak and Dagger used to reside. Here is where Morgana would also cast magic spells to try to turn Undertow back from a pirana to a tiger shark. Morgana has also stolen Ursula's Magic from Ursula's lair to turn Melody into a mermaid however, Morgana hasnt used enough of Ursula's magic on her so she could remaid a mermaid. The lair is caved in after Morgana's defeat by King Triton freezing her in eternal thick layer of ice. Undertow, Cloak, and Dagger's whereabouts are unknown.

Kingdom Hearts
Sora, Donald, and Goofy arrive on this strange new world after being given new magical forms by Donald that will allow them to survive and adapt; Sora becomes a merman with a dolphin tail, Donald becomes a half-duck cecaelia, and Goofy becomes a sea turtle. They quickly meet up with Ariel, Flounder, and Sebastian, and Sora quickly disguises the fact that they are not from this world by claiming that they are from a distant ocean. After teaching them to swim, the group is attacked by a group of Heartless, which Sora and his gang promptly dispatch. A concerned Ariel invites the group to visit her father's palace to see what to do. Taking them there, Triton dispatches more Heartless with his magic trident, dismisses Sora's questions about the world's Keyhole, and grounds Ariel. Sulking, Ariel sneaks off to her grotto, where she points out a mysterious mark on the wall. The party travels to the Sunken Ship, where they find a shining Crystal Trident that looks as if it might fit in the mark. After escaping Glut, a Great White Shark with a huge appetite, they take it back to the Grotto and place it on the wall, but before it can activate, Triton bursts in and destroys it. Ariel storms off, allowing Triton the opportunity to explain that he knows Sora and the rest are Keyblade bearers from another world. After proclaiming the Keyblade only brings destruction, he informs them they have no further business in Atlantica.

Meanwhile, Ariel is approached by Ursula, who promises the mermaid princess that she can help her get to "other worlds", but in order to do so, she needs Triton's trident; she also reveals during this time that Sora, Donald, and Goofy are from another world. Ariel steals it and gives it to Ursula, who uses it to injure Triton before retreating to her lair. Sora, Donald, and Goofy go in pursuit, and Ariel accompanies them, wanting to atone for their mistakes. Ursula escapes from her lair, but Ariel gives Sora a new power that will help him and the party get to Ursula and defeat her for good. Ursula receives a swift kick in the tentacles from Sora and his gang; they return the trident to Triton. He and Ariel open up the world's Keyhole, which Sora promptly seals.

Preceding this, Ariel asks Sora what his world is like, and Sora takes this opportunity to apologize for lying to her. Ariel forgives him with a smile, confident that she can find a way to travel to other worlds just as Sora had.

Kingdom Hearts: Chain of Memories
Sora, Donald, and Goofy arrive in Atlantica based on their memories. They run into Ariel who has stolen her father's trident to save her friend Flounder, who has been captured by Ursula to exchange for the trident.

They help Ariel rescue Flounder and eventually meet Ursula in a huge battle.

Kingdom Hearts II
In Kingdom Hearts II, the plot follows much to the original film. Like in the original film, Ariel is swimming on the surface shortly after a storm, and is horrified to see a young man, Prince Eric, floating on the remains of a ship. She brings him to the shore and falls in love with him, and, after singing a love song to him, returns to the ocean just as he regains consciousness.

Sometime later, Sora, Donald, and Goofy arrive and are reunited with Ariel, Sebastian, and Flounder; though Donald and Goofy quickly re-adapt to their sea creature forms, Sora has difficulty due to his year spent in suspended animation, so Ariel and co. help him. Sebastian then reveals that Ariel has been very depressed lately, and asks Sora, Donald, and Goofy to participate in the annual musical, hoping that their presence might get Ariel to lighten up. They agree, and perform "Swim This Way" fantastically, and once again meet Triton, who tells Sora in private that perhaps his participation in the musical will take Ariel's mind off her fascination with the human world.

However, things do not go as planned; even with Sora's presence, Ariel is unable to focus on rehearsals. Flounder then arrives and takes the trio to a statue of Prince Eric that he found, which is sure to cheer Ariel up. After acquiring the Magnet spell, Sora retrieves the statue and places it in Ariel's grotto, surprising her with it. Ariel then expresses her desire to walk on land in "Part of Your World", and Sora promises to help her in any way that he can.

After increasing the power of his Drive Gauge, Sora and Ariel perform spectacularly in "Under the Sea", a musical number which Sebastian hoped would "cure" Ariel's obsession with life on land. However, Ariel would prefer to sing about how the creatures of land and sea can live together in harmony, and ultimately decides not to sing at all when Sebastian shoots that possibility down, storming off with Sora, Donald, and Goofy in tow. Sebastian proceeds to complain about Ariel falling in love with a human at "the worst possible time"; unfortunately, Triton overhears him, and is not happy, especially given the fact that humans were responsible for his wife's demise.

Triton confronts Ariel, Sora, Donald, and Goofy in Ariel's grotto, angry with Ariel falling in love with a human. Ariel refuses to believe that all humans are as evil as Triton says, and Triton finally loses his temper; determined to turn Ariel over to his views of humans by any means necessary, he promptly destroys the statue that Sora retrieved for Ariel with a burst of energy from his trident and storms off. Distraught, Ariel runs off.

While moping in the courtyard, Ariel is confronted by Ursula, who has been resurrected by the powers of darkness. Ursula strikes up a deal with Ariel; in exchange for her voice, Ursula will change Ariel into a human being for three days. If Ariel can get Eric to kiss her within those three days, then the spell will be permanent; if she fails, she will return to mermaid form, and her very soul will belong to Ursula for all eternity. Sebastian and Flounder witness this, but are prevented from going for help by Flotsam and Jetsam.

Sora arrives, but it is too late: Ariel has signed the contract. Despite Sora's best efforts to stop her, Ursula magically draws Ariel's voice into her shell necklace and transforms the mermaid princess into a human. Ariel, no longer able to breathe underwater, begins to drown, but Sora quickly grabs her and pulls her to the surface while Ursula laughs.

Sora drags an unconscious Ariel to the shore, where she is confronted by Eric himself and accepted into his home. Sora, Sebastian, and the rest unanimously agree to keep Triton in the dark about Ariel's situation, and spend the time watching Ariel's progress; at one point, Ariel and Eric nearly kiss, but are stopped by Flotsam and Jetsam rocking their boat (though Sora and co. don't see this happen). When not watching over Ariel, Sora, Donald, and Goofy also spend the three days looking for Ursula in the hopes that they can force her to reverse the spell, but are unable to find her.

Near the end of the final day, Sora and co. check up on Ariel, and see her crying at the beach. At that moment, Eric, having seemingly been hypnotized, walks to the beach alongside a black-haired girl singing in Ariel's voice. Seeing the girl wearing Ursula's necklace, an enraged Sora puts two and two together and uses a burst of energy from the Keyblade to destroy the necklace, breaking Ursula's hold over Eric and restoring Ariel's ability to talk. Eric realizes that Ariel is the girl who saved him, but before they can kiss, the sun sets; Ariel has missed the deadline. Ursula reverts back to her normal form and grabs Ariel, returning to the sea with Sora, Donald, and Goofy in hot pursuit.

In the confrontation that follows, Triton arrives and attacks Ursula, but she reveals that even he doesn't have the power to break Ariel's contract. With no other choice, Triton agrees to take Ariel's place, and is transformed into a polyp as the horrified Sora and co. watch. Ursula promptly takes Triton's crown and trident and proclaims herself the queen of the sea, moving to finish Triton off. Ariel, restrained by Flotsam and Jetsam, demands that Ursula let everyone go, but at that moment, Eric arrives and hits Ursula in the arm with a harpoon. Flotsam and Jetsam charge at Eric, but Sora, Donald, and Goofy block their path. Enraged, Ursula once again transforms into a giant and engages Sora, Donald, Goofy, Ariel, and Eric in combat.

Throughout "Ursula's Revenge", Sora, Donald, Goofy, Ariel, and Eric work together to fight Ursula, once again eliminating Flotsam and Jetsam in the process. In the end, Sora knocks the trident out of Ursula's hands, and Eric impales Ursula with it, destroying her once again.

In the aftermath, Ariel reveals her mermaid form to Eric, and sadly states that they cannot be together. Eric, however, states otherwise, and both embrace. In the end, Sebastian goes along with Ariel's idea for the musical through "A New Day is Dawning", in which Ariel proclaims her newfound happiness.

At that moment, King Triton's Trident begins to glow, and Sora uses the Keyblade to open another pathway. Though Ariel is sad that they have to leave again, Sora, Donald, and Goofy refuse to say goodbye and assure Ariel through a musical number that they will meet again.

Trivia

 * Although the kingdom is known as Atlantica, it was never referred to as that in the original film. It wasn't until a novelization released in 1993 that the termed was coined. The TV series was the first animated medium to utilize that name. The name would stick in the sequel and other Disney media afterwards.
 * Using images from the prequel movie Ariel's Beginning, it can be assumed that mermaids do not receive their sea-shell bras until they are teenagers (as the oldest of Ariel's sisters are pre-teens and are repeatedly seen wearing bandeau like breast bands).
 * It is most likely off the cost of Denmark (Hans Christian Anderson appeared in an episode of The Little Mermaid Animated series).