Much of The Grid is designed the same. The beginning area for Sora, the City, features numerous tall structures, streets, crosswalks and large slopes that allow vehicles passage to the Throughput.
The Throughput appears similar to an urban, digital plateau, with numerous hexagonal and octagonal platforms risen. Beyond this area is the Bridge, a closed area that encompasses only part of the long-passing bridge of Tron City. Taking the Recognizer in the previous area, one is led to the Docks, a large hexagonal platform with a central elevator and two Solar Sailers ready for departure, the upper levels of this area feature a number of turrets, locked gates and another elevator. Taking the Solar Sailer, you are led into it.Numerous cargo containers are open with turrets that must be destroyed to fully explore this area. Ahead of this is the Rectifier: 1F, the first floor of CLU's massive ship. A large amount of cargo containers are scattered in the area, with some planes along the side, a small hall to the left is the entryway to the Rectifier 2F, the second floor of CLU's ship which is a number of walkways above the first floor with a Recognizer that allows passage to an area non-accessible by foot. Additionally, there is an elevator in the area that leads to the Throneship, CLU's personal command ship. It has three rooms, the first being the entry, colored orange, the second being a light blue but darkly-lit room where numerous Black Guards spawn and finally, a large triangular-shaped orange room that houses Flynn's Identity Disk.
Among these areas are four areas that are not exclusively part of the city, the first is the Stadium, a small octagonal area where Sora battles Rinzler. The Portal: Stairs, a long path with numerous turrets and a save point and the Portal, a large circular platform. Finally, there is the Light Cycle Arena, a wide arena with a race track encompassing it.
Between Kingdom Hearts Birth by Sleep and Kingdom Hearts
Before Radiant Garden's fall, Ansem the Wise had come upon the Grid and copied its data at the time to create Space Paranoids for both his world's town maintenance and for his personal research. When the Heartless began invading the Realm of Light, The Grid was one of the worlds that was swallowed in darkness. Although it was freed from the Realm of Darkness after Sora defeated Ansem and purged the End of the World, The Grid remained asleep as one of the Sleeping Worlds, plagued by Nightmares.
Sora comes to in this world and, seeing his clothes, believes to be back in a familiar world. He spots a Recognizer and chases after it. Soon, several Black Guards attempt to arrest him, identifying him as a stray program, but he escapes. He soon encounters Rinzler and they prepare to fight, but Rinzler suddenly leaves. Sora is then met by Kevin Flynn, his son Sam, and Quorra, who is fascinated by Sora's Keyblade. When Sora mentions that he knows Tron, Flynn explains that the figure that Sora encountered was Tron, reprogrammed by CLU to serve him. Sora offers to restore Tron, and Quorra agrees to take him to the Rectifier.
The two of them take a Solar Sailer to the Rectifier, where they are ambushed by Rinzler. Sora attempts to get Rinzler to remember his past as Tron, but Rinzler suddenly counterattacks, then kidnaps Quorra. Sora is confronted by the unknown youth, accompanied by Xemnas, who explains that this is the world where Ansem got the data for his own computer, then muses about the nature of data and memory, asking Sora if he is sure his memories are his own before leaving through a Dark Corridor. The mysterious youth opens the doors behind Sora, cryptically telling him that data cannot dream and that this is not a dream, but reality. Sora is blown out the doors by the wind, finding himself in the Disk Wars stadium, where he encounters CLU and Rinzler. CLU offers to release Rinzler in exchange for the Keyblade, but Sora refuses. Rinzler attacks Sora, who fights back when Quorra tells him he can get through to Rinzler.
Sora defeats Rinzler and reprograms him, but CLU appears and attempts to take out Sora with his Disk. Rinzler manages to push Sora aside and deflect the hit, but the ricochet takes out the floor beneath him, causing him to fall below the stadium, failing to reach Sora's outstretched hand. CLU then leaves to recapture Rinzler, saying he'll deal with Sora later. Sora is saddened from failing to save his friend, but Quorra comforts him.
Shortly after, while considering Xemnas's words, Sora finds the Grid's Keyhole and unlocks it.
Upon entering the Grid, Riku notices his new clothes and wonders whether the world is special. He is soon confronted by several guards, who identify him as another stray program. To learn more about the world, he allows himself to be captured by the guards. He is transported on a Recognizer along with Sam Flynn, who tells him where he is. Riku brought to the Light Cycle track, where CLU pits him against several Black Guards on light cycles, and during the race battle, the Commantis appears on the track and attacks. Riku fends it off, then escapes the track by blasting a hole in a wall.
He meets up with Sam, who tells him about his father, who has been stuck on the Grid for twenty years, hiding from CLU. The two of them head for the Portal leading to the real world, where Sam plans to delete CLU. Sam goes on ahead for a bit, and Riku later catches up with Sam, Kevin, and a catatonic Quorra. The group head for the Underground Docks to take a Solar Sailer to the Portal, and on the way Riku watches Flynn repair Quorra while he talks about the nature and origin of the ISOs, of which Quorra is the last, and how his and CLU's search for perfection led to their destruction. Riku reflects on how Flynn's story compares to Xehanort's, how their single-minded curiosities led to destruction and pain.
CLU's forces located them and force them onto a new course, but Quorra gets herself captured to give the others a chance to reach the Portal. Sam and Riku head off to CLU's Throneship to recover Flynn's Identity Disc and rescue Quorra, while Flynn goes to commandeer a ship. Although they recover the disc, Rinzler arrives with Quorra in custody. Sam and Riku attack Rinzler, with Riku knocking him off the ship with a Wall Kick. They take Quorra and join Flynn on a glider, which they take to the Portal.
There, they encounter CLU, who summons the Commantis to stop them from going further. Riku takes on the Dream Eater in battle and destroys it. While Flynn baits CLU with his disc, Sam and Quorra head for the Portal. However, CLU discovers that Flynn switched discs with Quorra, and he attempts to jump the now-open bridge to the Portal. Sam uses Flynn's disc to activate the Portal, and when CLU tries to enter it, even with Riku blocking his path, Flynn suddenly draws CLU to him and absorbs him, disappearing in the process. The Portal closes with Sam and Quorra on the other side, and the Keyhole appears to Riku as he contemplates the significance of Portals.
Like in Space Paranoids, Sora and Riku are converted into data and change forms accordingly. The forms resemble the outfits worn by other characters in the film. They both wear dark blue suits with light blue circuitry and visors characteristic of participants in the Grid's Disk Wars competition. Sora's form also slightly resembles his Kingdom Hearts II design, but without the prongs.