Cavern of Remembrance

The Cavern of Remembrance is an area of the world Radiant Garden that was introduced in Kingdom Hearts II Final Mix. It is filled with extremely powerful Heartless and Nobodies, and also focuses strongly on the use of in opposition to the rest of the game. The main attraction of the area is the Organization XIII's Replica Data battles contained at its terminus.

Settings and Areas
The hole in the castle wall at the Postern reveals a broken ladder leading into the Saishinbu (最深部), which at first appears to be small cave with a stream of water pouring down a high ledge, next to a Valor Form crystal. However, past the ledge is a short tunnel leading to an immense, beautiful crystalline cave, containing many ledges, stalactites, and stalagmites which can be ascended to reach an ornate door, as well as a healthy population of powerful Heartless.

Through this door lies the lowest part of the Kōdō (坑道), a deep, winding which is crisscrossed with pipes across multiple "floors". Each floor contains openings in the pipes that require specialized, maximum level Growth Abilities to traverse, as well as the appropriate Drive Form crystal for each obstacle; the first two are also guarded by event battles with several waves of Heartless. Crossing the first chasm with Quick Run brings Sora to another ornate door, as well as a passage leading to an upper cubby of the Depths, where he can dislodge a stalactite in order to create a shortcut. The second floor of the Mineshaft, which can be accessed through the Mining Area, and has pipes can be bypassed with Aerial Dodge in order to reach an additional door to the Engine Chamber.

Both the door and the cubby lead to the Saikōbu (採鉱部), a complex area of pistons, vents, and engines that is initially inert. By activating the engines lying at the very bottom of the chamber, Sora awakens the powerful machinery that he must negotiate to reach the next door.

Through this door is the busy Kikanbu (機関部), filled with conveyor belts, pistons, scalding jets of steam bursting from pipes, and more powerful Heartless, as well as several hidden balconies. At the end of this is another door and another section of the Mineshaft, with a final pipe obstacle which must be threaded using Glide.

Exiting the cavern through this door brings Sora to the Tsuioku e no Izunai (追憶への誘い), a long balcony hallway built in the same style as Castle Oblivion, with Radiant Garden's characteristic inverted waterfalls against the open sides of the path. The hall is filled to bursting with powerful Nobodies, and Sora's initial traversal of it requires him to conquer three separate event battles, each with multiple waves of Nobodies.

The final door brings him out of the subterranean caves to the Garden of Assemblage, which can be used to bring to face against the Organization XIII's Replica Data as well as a secret passageway, veiled by an illusion, back to the Restoration Site.

Gameplay
The balloons filled with Drive Orbs at certain points of the Cavern of Remembrance indicate that Sora must use the Drive Form abilities to get past a certain area. Sora needs to use High Jump (acquired from Valor Form) to get over the wall at the entrance (hence the red coloration). At the entrance of the Mineshaft, Sora needs to use Quick Run (acquired from Wisdom Form), hence the blue coloration of the balloons, and so forth. Whenever Sora enters into the corresponding Drive Form, the balloons light up. These balloons drop large quantities of Drive Orbs when attacked, making them ideal for leveling Master Form.

After the Transport to Remembrance is cleared the first time, the enemies that spawn within will vary each time the room is entered. Sorcerers, Snipers, Dragoons, and Creepers appear in one group, while Berserkers, Assassins, Dancers, and Samurai appear in the other.

It is possible to go through the Cavern without actually getting the High Jump ability or the Dodge Roll ability. One just needs to have Aerial Dodge and Glide, for if they fall at the entrance and climb up the rocks in the first room. Also, Master Form's Aerial Dodge will enable the player to jump to the door of the first area of the Cavern without touching the ground level, preventing Heartless from spawning in that room. It is also possible to advance the Cavern without having Wisdom Form and Master Form at their maximum levels by entering Master Form in midair, then immediately using the Aerial Dodge ability to travel extra height or distance. To carry out this trick successfully, before performing the jump, the Command Menu cursor should be on the Drive command and Master Form should be selected within the Drive menu. Hence, Sora can enter Master Form very quickly by pressing twice.

Kingdom Hearts II
Shortly after Sora, Donald Duck, and Goofy hear an explosion coming from outside the castle, they run to the entrance and find a hole in the nearby pillar. They see Yuna, Rikku, and Paine flying out of the hole. Sora is curious as to what is inside the hole, but Donald yells at him, telling him that they can check the area later, and that they have to go after the King, as the Heartless are invading. Sora may access the Cavern at any time after this.