Hollow Bastion is a world in Kingdom Hearts and Kingdom Hearts: Chain of Memories, and called Hollow Bastion I in Kingdom Hearts coded. In Kingdom Hearts II, the world was expanded into the town and other areas. It appeared in a flashback to events from Kingdom Hearts experienced by Xion in Kingdom Hearts 358/2 Days.
Not based on a Disney film, though showing Disney influence such as the Beast's haunted castle from the movie, Beauty & the Beast, and Maleficent's fortress from the Forbidden Mountain from the film, Sleeping Beauty, Hollow Bastion is a colossal castle that towers above the rest of its world, Radiant Garden. At one point, it was the only remaining part of the world, along with the waterways beneath it. Because of this, the world itself was known as "Hollow Bastion" in Kingdom Hearts, Kingdom Hearts: Chain of Memories, and most of Kingdom Hearts II. However, it regains its original name of Radiant Garden by the end of Kingdom Hearts II, when Tron used his powers to show what the world was like before its destruction.
Unlike the rest of the Radiant Garden, which poses as Final Fantasy's world, Hollow Bastion has no relation to Final Fantasy whatsoever.
 Settings and Areas
 Kingdom Hearts
Sora and the rest of the party enter Hollow Bastion at the Rising Falls, appropriately named as there are waterfalls that run up instead of down. Jumping on mystical floating rocks and ledges takes the party to the first of many magical platforms that are scattered throughout the castle. The platform takes Sora to the Castle Gates, the main entrance of Hollow Bastion which is made up of a set of balconies and lifts running outside the castle. From here, the party can travel down into the underground water system or enter the castle itself.
Going down the nearby platform or leaping off the edge of the balcony takes the party to Base Level, an area full of ledges, switches, and enemies. Successfully climbing to the balcony near the entrance earns extra treasures, while taking a nearby bubble carries them to the Waterway, where a series of gates, switches, and bubbles must be navigated to operate the castle gate controls. Off of the Waterway is a small room, the Dungeon.
Going in the doors at the other end of the Castle Gates area takes the party to the massive two-level Entrance Hall, where a fight against Riku takes place. To continue onwards through the castle the puzzle at the end of the hall must be solved; solved, it allows access to the second half of the Castle Gates. Taking the left door in the Entrance Hall leads the party to Library, also the site of a large puzzle involving organizing misplaced books. Belle, Yuffie, Leon and Aerith can later be found here after the Hollow Bastion Keyhole is locked. Also accessible from the Library is the first of many entrances to the Lift Stop, a series of magic lifts separated by mystical barriers. The ceiling of the Lift Stop is decorated like the stained glass that characterizes the Station of Awakening.
Continuing up the castle by taking the lift on the other side of the Castle Gates area is the Great Crest (an enormous Heartless emblem), where the largest of the magic lifts is located. After a long and slow journey across the front of the bastion, the party is dropped on the other side, where they can take the Lift Stop to the next area, the High Tower, where a smaller crest can be moved to create a way up to the upper levels of the castle. Through the Lift Stop at the opposite end of the High Tower is the entrance to the Castle Chapel, where the exit to the next room is sealed until Maleficent is defeated. There is also a secret area, where you fight the Dragon and Xemnas.
Once the seal is broken, the party arrives in the Grand Hall, where the Princesses of Heart are held captive and the Keyhole to Darkness forms. Inside the Grand Hall is a Heartless Emblem-shaped portal leading to a small dimension known as the Dark Depths. Here, Sora and company fight off the Behemoth guarding the Keyhole from being sealed.
In the End of the World's World Terminus, Sora is transported to an unseen section of what is supposedly Hollow Bastion. All that is there is a hallway that appears similar to the corridors near Ansem's study in Kingdom Hearts II. One end of the hall fades to darkness in the distance, leading back to the World Terminus. The other end has a giant Heartless emblem floating in it, not allowing passage. To the left of the entrance is a chamber with a strange apparatus and multiple holes of darkness. It has a large computer and several human-sized pods attached. This may be where Xehanort and his cohorts tore their hearts from their bodies and became Heartless. The computer has a message that must be read before Sora can leave;
Riku's Room is an area not available to Sora that is revealed during Riku's journey in Kingdom Hearts: Chain of Memories.
 Kingdom Hearts II
Access to the castle is very limited in Kingdom Hearts II. During the second trip to the world, the way to the castle is unlocked and leads to the Postern, the site of a save point and the base entrance to the bastion itself. Going inside, the party must navigate the twisting Corridors before reaching the end at Ansem's Study, where many of the mysteries surrounding Ansem can be solved, but many more created.
Despite promotional images and movies for Kingdom Hearts II that depict Sora, Donald, and Goofy in battle in the High Tower area of the castle as it appeared in Kingdom Hearts, the area is nonexistent in the second game.
 Ansem's study and computer
Ansem's Study was the private study of Ansem the Wise in Hollow Bastion. The room contained a throne and desk, containers filled with hearts, and books. As leader of Radiant Garden, he used it to store his research on the heart. Mickey Mouse and Ansem often talked in there. There was a portrait of Xehanort in the study, though it is unknown if Ansem or Xehanort put the painting up there. Behind the painting, it shows the password which are the Princesses of Heart. There was a secret passage in the wall that leads to Ansem's Computer.
Ansem's Computer is a complex computer system used by Ansem the Wise during his rule over Radiant Garden, and later used by his apprentices after his exile. It contains an elaborate network copied from ENCOM, containing the Space Paranoids world, which was updated and modified for research purposes.
The computer once held a vast variety of infromation regarding many subjects studied by Ansem and his apprentices, such as the Heartless, Nobodies, the Organization, and Ansem the Wise himself. However, when Sora, Donald, and Goofy tried to access the infromation on their enemies, they found that all of it was corrupted (possibly by Xemnas). The only thing that did come up was a picture file of the true Ansem the Wise, leading to the truth being revealed about Xehanort's Heartless.
The computer continues to be used by Xemnas to access the Chamber of Repose located several miles below the factory. It also allows access to the Heartless Manufactury on the floow below the room, and activates the laser that transports users to Space Paranoids. On the other side of the computer room is the small, but often missed Heartless Manufactory.
 Kingdom Hearts coded
In Kingdom Hearts coded Hollow Bastion I is very similar to the Hollow Bastion from Kingdom Hearts. Data-Sora starts his journey in the Castle Gates, he then goes to the Waterway as soon as he finds the gate is locked shut to find a way to unlock the gate. After opening the gate, he soon joins with Goofy at the Entrance Hall (LL). After examining the Heartless slot on a door, Data-Sora and Goofy visit the library, which is broken down into Library 1, Library 2, Library 3 and Library 4, to search for the missing emblems. Data-Sora also chases after Donald in the Waterway. After the party is set, they travel to the Great Crest via a huge lift, leading to the High Tower. After obtaining the last emblem, they can finally chase after Pete who waits in the Grand Hall. Data-Sora encounters Pete and Data-Riku in the Keyhole, at the Chapel.
 Kingdom Hearts Birth by Sleep
During his time in Radiant Garden, Ventus sees his friend, Mickey, in the distance and gives pursuit. His chase leads him to one of the doors of Hollow Bastion, guarded by Dilan and Aeleus, who appear to be asleep. When Ventus approaches, they suddenly wake up and deny him entry, instead telling him to go home before the Unversed harm him. When the Trinity Armor appears, Dilan and Aeleus prepare to aid Ventus against it, but Even appears and orders them to carry on guarding the castle.
 Between Kingdom Hearts Birth by Sleep and Kingdom Hearts
Hollow Bastion was once a glorious castle towering over the Radiant Garden and owned by a respectful king, Ansem the Wise. Much of the history of the castle is unknown, other than that Ansem ruled from it. However, eventually Ansem's apprentices led by Xehanort overthrew their former mentor, and furthered Ansem's original drives to include more mechanical components. The result is a twisted bastion; half beautiful castle, half distorted factory. According to Leon, Maleficent invaded Hollow Bastion's world with her Heartless nine years before the events of Kingdom Hearts. Some residents managed to escape, many of whom end up in Traverse Town. However, the youngest known resident, Kairi, is sent into the oceans of the worlds by Xehanort and ended up in Destiny Islands due to Aqua's spell. During her reign in the castle as one of Ansem, Seeker of Darkness's minions, it is probable that Maleficent either created or remodeled the castle's keep, which has decorations and models of roses and her thorned plants.
 Kingdom Hearts
Sora, Donald and Goofy arrive at Hollow Bastion in time to find Riku attacking another intruder, the Beast. Sora, Donald, and Goofy confront Riku, but he declares he is the Keyblade's true holder; it jumps into his possession, leaving Sora defenseless except for his old wooden sword. Shocked at this revelation, Sora collapses to the ground. Riku departs, and Donald and Goofy, having been ordered to follow the Keybearer, reluctantly follow him. The Beast staggers on despite his injuries, and Sora quickly gets over his shock to help him. The Beast reveals that he is looking for someone important to him, and refuses to depart without her. Sora, sympathizing, takes up his old wooden sword, and the two team up to enter the castle.
After traversing the castle waterways to unlock the main door, Sora and Beast enter Hollow Bastion. Beast witnesses an illusion of Belle transforming into a Heartless, and, enraged, jumps at the Heartless, with the doors slamming shut behind him. Riku, Donald, and Goofy appear soon after, where Riku orders Sora to give up, though Sora refuses to leave without Kairi. Sora informs Riku that while the darkness may destroy his body, it can't harm his heart, and Riku decides to test Sora's theory by firing a Dark Firaga attack at him. Sora, believing it to be the end, braces himself, but Goofy rushes in and blocks the blast with his shield. After being questioned by Riku, Goofy swears that he will never betray King Mickey, but won't betray Sora after all that they have been through together, and asks Donald to apologize to the King for him; however, Donald also chooses his friendship with Sora over King Mickey's orders and rejoins Sora. Sora informs Riku that he doesn't need the Keyblade; his friends and heart are the only weapons he needs. Sora's strength of heart with his friends back by his side pulls the Keyblade away from Riku and back to him. After a fierce battle, Riku is defeated and flees. Beast rejoins the party after watching the encounter, observing that Sora's heart was what helped him win.
Riku is upset at losing the Keyblade, but encounters Ansem, Seeker of Darkness, who promises him that he can make Riku's heart stronger through darkness and allow him to regain possession of the Keyblade. Jealous and angry at Sora and shamed over his loss of control of the Keyblade, Riku succumbs to his pledge and powers, and becomes consumed by the darkness. In the meantime, Maleficent has attempted to use the gathered Princesses of Heart to open the Bastion's Keyhole. The Heartless-possessed Riku meets with her to check her progress, where Maleficent declares she will control and use the darkness for her own purposes; however, neither she nor Ansem-Riku can unlock the Keyhole without Kairi's missing heart.
Sora and friends manage to travel through the labyrinth of a castle to reach the chapel; there they meet with and confront Maleficent. Overconfident in her abilities and underestimating those of Sora's gang, she is soundly defeated. Escaping back to Riku for help, she is stabbed through the heart by his Keyblade of People's Hearts, made from the hearts of the six Princesses. It unlocks the darkest parts of her heart and allows her to transform into a large, powerful dragon; however, Sora's party defeat her again, and she is consumed and burned away by the darkness. Riku then appears and reveals that Maleficent was merely a pawn of the Heartless, unable to see the darkness swallowing her heart. He then departs and Sora and company travel to the Grand Hall, where the Keyhole and Princesses are located, to find and confront him. There, Sora finds Kairi unconscious on the floor in front of the partially opened Keyhole. He tries to wake her, but Riku appears to tell Sora her heart is missing. Riku continues to tell Sora that Kairi is one of the princesses and that her heart is within him. Sora is able to realize that Riku is no longer in control of his own body. Riku knocks both Donald and Goofy back behind a preset barrier, and Kairi's heart reacts to the Keyblade of People's Hearts' power, causing Sora crippling pain. Xehanort's Heartless then attacks him, but Sora recovers and blocks the strike in time. After an intense battle over who would possess Kairi's heart, Sora emerges victorious.
Riku disappears, but the Keyhole begins reacting to the presence of Kairi's heart. Sora attempts to lock the Keyhole, but without Kairi's heart, it is not complete and cannot be sealed. Sora puts two and two together and realizes what he has to do; despite Donald and Goofy's desperate pleas, Sora stabs himself with the Keyblade of People's Hearts left in Riku's wake, releasing all of the princesses' hearts (including Kairi's) and completing the Keyhole, but Sora falls into darkness himself.
Kairi wakes just in time to see Sora disappear. As Kairi, Donald, and Goofy mourn the loss of Sora, Ansem, now in full possession of Riku's body and having shaped it into one resembling his original human self, reappears, declaring that Kairi's purpose is over, effectively deciding to kill her. Donald and Goofy bravely make a stand against Ansem, but both know that, without Sora, they may not be able to stop him. However, before Ansem can attack, Riku projects himself from his stolen body, manages to establish enough control to stop him in his tracks, and warns Kairi and the others that the Heartless called by Ansem will soon overrun the castle at which they heed and run to escape. The three return to the entrance, and hesitate due to Kairi's reluctance to leave Sora and Riku behind; Goofy himself is still concerned about the Keyhole (apparently failing to realize that, without Sora and the Keyblade, the Keyhole cannot be stopped). An apparently non-hostile Heartless arrives; Donald shouts at it to get lost and whacks it over the head with his staff, but Kairi realizes that the Heartless is, in fact, Sora. At that moment, massive legions of Heartless attack, and swarm Kairi and Sora's Heartless, much to Donald and Goofy's horror. However, a brilliant flash of light blows the Heartless back, and in place of the Heartless, there is Sora, fully restored. Beast stays behind to hold off the Heartless and continue looking for Belle, and so the group departs Hollow Bastion.
Cid manages to find a way to allow them to return and seal the Keyhole. They return and help Beast reunite with the re-awakened Belle, and jump through the Keyhole to fight a Behemoth Heartless. After a conversation with Leon's group, who have returned to restore their home world, Sora seals the Keyhole at Hollow Bastion.
In the Kingdom Hearts Final Mix version, Sora also has his first encounter with Organization XIII in the chapel by way Xemnas, here known only as "Unknown". After some cryptic messages (such as stating that Sora is incomplete and looks just like "him"), Xemnas departs. It is revealed in Kingdom Hearts II that this battle takes place shortly after Xemnas recruited Roxas into the Organization, and he fought Sora to test his abilities.
 Kingdom Hearts: Chain of Memories
In Sora's story, Hollow Bastion is also recreated as a figment of his memory. It is where the Beast, Belle, and Maleficent which were created from his memory are, and Belle is denying her love for the Beast and Sora has to defeat Maleficent in her Dragon form. But opposed to the first game, it focuses more on the relationship between Beast and Belle.
In Riku's Story, Hollow Bastion is recreated inside Castle Oblivion as a figment of his memory. It is the first world he enters and fights a memory recreation of Maleficent in her Dragon form.
A statue appears here in the Entrance Hall that was not present in Kingdom Hearts.
 Kingdom Hearts 358/2 Days
During Kingdom Hearts 358/2 Days, when Roxas experiences a short sequence of Sora's memories, the keyhole to Hollow Bastion can be seen as Sora releases his heart and his body dissipates.
 Kingdom Hearts II
 Kingdom Hearts coded
After Maleficent destroys Data-Sora's Keyblade in the datascape's version of Agrabah and captures Data-Riku, Pete takes Data-Riku to the datascape's Hollow Bastion. Without his weapon, Data-Sora is unable to fight, so Mickey travels there himself, leaving Donald, Goofy, and Data-Sora at Disney Castle. However, Sora runs off to Hollow Bastion on his own to confront Pete, and he manages to unlock the castle gate while dodging Heartless. Inside, Pete traps Sora and summons a horde of Heartless to attack, but Sora is rescued by Goofy. The two of them begin searching for a way to follow Pete deeper into the castle, while searching for Donald, who got separated from Goofy when they entered Hollow Bastion.
Sora and Goofy find Donald in the waterway, and the three of them explore the castle, with Donald and Goofy breaking Bug Blox and fighting Heartless in place of Sora. They find the pieces of the Heartless emblem that unlock the door leading to the upper levels of the castle, and at the High Tower, Data-Sora reflects on the bond he feels with Donald and Goofy. The three of them confront Pete in the Grand Hall, where he traps Donald and Goofy in a cage of blox. Desperate, Sora manifests a new Keyblade from his evolving heart and frees them. Pete retreats into the Keyhole, followed by Sora, who defeats him despite his own powers in the datascape. Pete then sets Data-Riku on him, having corrupted his data with bugs, but Data-Sora manages to subdue his friend after a drawn-out battle.
Although Data-Sora and Data-Riku emerge from the Keyhole, Riku's data is thoroughly corrupted, prompting Sora to enter Riku's personal datascape to destroy the bugs, in Hollow Bastion II. After visiting manifestations of Riku's memories of different worlds, Sora defeats the main source of the corruption, which takes Riku's form. Maleficent attempts to block Sora from returning from inside Riku's data, but he emerges, and he defeats Maleficent's dragon form in the chapel. Mickey, Donald, and Goofy say goodbye before returning to the real world, but when the datascape begins erasing itself, Data-Sora sets off through the Final Keyhole for the innermost part of the datascape to retrieve Maleficent and Pete and to confront the source of the corruption.
As Data-Sora progresses through the datascape's Castle Oblivion, he enters a room based on his visit to Hollow Bastion. He chases after Pete, using switches to progress, and defeats him. Pete calls Maleficent, who brings them to a long, trap-filled room, forcing Sora to traverse the obstacle course to reach the far side of the room. Upon confronting the two, Sora is returned to the Entrance Hall, with an Ending Card for Hollow Bastion.