An artificially generated digital environment, powered by a quantum supercomputer hidden underground below the old Renault Auto Factory and housed in an ultra secure shell floating in the bottom of the Digital Sea. Lyoko is constantly changing its position on the Network due to its outer shell floating in the Digital Sea's turbulent currents, and it requires a special homing address to interface remotely with from the real world or physically locate from the digital one. It is segmented into four sectors, each with their own environment, and a core sector in the middle that holds the codes that keep Lyoko together.

After XANA stole the "Keys to Lyoko" from Aelita and escaped Lyoko's confinement into the greater Digital World, he began targeting the core data of the virtual environment to try and destroy it and prevent Team Lyoko from using it against him. Part of this included deleting surface sectors by possessing Aelita and using her to take control of the Way Tower in each, as the Lyoko Warriors needed the surface sectors to get to the core sector of Sector Five until Jeremy eventually created direct virtualization there.

Nonetheless, even then, XANA succeeded in destroying Lyoko when he took possession of a rookie Lyoko Warrior named William Dunbar, but Jeremy began work on recreating it after receiving an e-mail from Lyoko's creator, Franz Hopper, who was hiding somewhere else in the Digital World He managed to recreate the outer shell and Sector Five by the time William returned, still under XANA's control, and the Lyoko Warrior's Digimon partners started to make themselves known. After that, he managed to build back each surface sector one by one with the blueprints in Hopper's e-mail and newly available resources from the greater Digital World.

Sector Five is really only called that because it was the fifth sector discovered by the Lyoko Warriors, though it was really the first sector to be created both in Lyoko's original incarnation and its recreation following the original's destruction. Sector Five is the core of Lyoko, housing all of its fundamental codes that hold the environment together. The outermost shell of the sector is an enormous white sphere directly in the middle of the four surface sectors that binds them together, before Lyoko's destruction by webs of thick cables and after by a strong wireless bond. The inner walls of the shell is a massive, blue swirling current of source codes that can be extremely dangerous to fall into. Suspended in the middle of the massive hollow within the outer shell is a blue inner shell about half the size but no less impressive in its own scale, the space then referred to as the Celestial Dome. White tunnel-shaped data bridges link the outer and inner shells on four sides, leading to and from inside the inner shell to each of the four surface sectors; these bridges can be opened to allow one to fly out into the corresponding surface sector from the Celestial Dome. The sphere housed by the inner shell is built primarily of many, many blue blocks that form rooms and mazes throughout, with a big Arena in the center featuring the Eye of XANA in white stretched out across the circular floor. The Arena is where a special transport orb between Sector Five and the other sectors drops off passengers going to the sector and picks them up when they're leaving it. Directly below the Arena is an orb containing all the most vital codes that shape Lyoko, called the Core of Lyoko, suspended at the top of a tall room only accessible by a rapidly opening and closing port hole on the south pole of Sector Five's inner shell. After XANA freed himself from the confines of the supercomputer, he attempted repeatedly to destroy Lyoko by wiping out the Core of Lyoko, and he finally succeeded after possessing rookie Lyoko Warrior William Dunbar to perform the deed.

The area of blue blocks within the inner shell and surrounding the Arena and Core of Lyoko room is referred to as the Core Zone. In Lyoko's initial form, the Core Zone would constantly shift and lock individuals in or out if a special key, in the form of an Eye-shaped button, wasn't activated within the three-minute countdown activated any time someone enters the Arena from outside of the sector. The upper half is well lit and contains, between mazes and hallways, a couple different rooms can potentially contain different things, one such housing the sector's only Tower. Elevator platforms are used to reach different levels of the Core Zone, which includes a large garage area in the topmost area of the Core Zone created to hold the digital submarine the Skidbladnir, which Team Lyoko created starting immediately after recreating every sector and sometime after meeting their Digimon partners. An elevator on the outermost layer of the Core Zone takes its passengers to a pathway out onto a catwalk sticking out of the sector's inner shell and over the Celestial Dome, and an interface screen that has access to the sector's data can be opened at the end of this catwalk. The lower half of the Core Zone is a darker, less stable, couple of wide rooms built more shoddily from Sector Five's blue blocks than the upper floors and is barely used.

Built in 1926 under Louis Renault, French industrialist and the founder of the Renault Group automotive company, the Renault Auto Factory is a massive complex that covers nearly the entirety of Seguin Island, a stretch of land in the Seine River by the western Paris suburb of Boulogne-Billancourt. Forced to make trucks for the Germans during France's occupation in World War II, the factory was subject to multiple Allied bombings during the course of the war. As such, when the factory was rebuilt following the war's end, Renault secretly had a multi-layer bunker built below the factory to quickly evacuate important documents and personnel to if the factory would ever be attacked again. Despite being caught in the middle of the political and economic power struggles in postwar France, the Renault Factory continued to thrive until the Renault Group shut down the factory in 1992 and moved to newer ones.

Waldo Schaeffer, under the alias of Franz Hopper, scouted the factory out shortly after and hired a small family construction group named Broulet & Brothers to retrofit the bunker below into a lab for a quantum supercomputer he intended to build and use against an old project he walked out on for ethical reasons, Project Carthage. The supercomputer was programmed to sustain Lyoko, a multi-sector environment enclosed in a secluded part of the Digital World, and it also housed an A.I. named XANA. After Franz Hopper and his daughter, Aelita, fled to the factory and Lyoko to escape agents sent by former Project Carthage colleagues, only to be turned on by XANA, Franz shut off the supercomputer from the inside, and the factory went abandoned once more.

It was nearly ten years later that Kadic Academy student Jeremy Belpois would find the supercomputer, turning it on. He, Ulrich, Odd, and Yumi would become allies to Aelita and enemies to XANA, declaring themselves the Lyoko Warriors making the factory a sort of secret base of theirs in the process. They typically reach the factory via a secret passage through the sewers that leads up to the Daydé Bridge, a large suspension bridge connecting Seguin Island to the mainland. XANA would use the abandoned machinery of the factory against the Lyoko Warriors on a few occasions. These would include building killer robots with the auto assembly lines on one occasion and attacking them directly with the machines in another.

The factory floor, also known as the cathedral, is the enormous two-story space that makes up the main room of the factory. The stretch of space is lined by a balcony that is held up by sturdy steel support beams and overlooked by now dirty (and broken in some cases) windows. The bridge connecting to the factory leads directly through a large open garage door, above which hangs a rusty old sign that still reads "RENAULT". There are two means of safely reaching the lower area of the cathedral from the balcony. One is a set of three sturdy ropes hanging from the ceiling just past the broken remains of the staircase that previously led downwards. The other is a vehicle ramp located by turning left on the balcony when coming in through the main door.

Just right of where the original stairway once stood when entering is the elevator shaft leading down to the bunker containing Franz Hopper's equipment. The bunker was originally only accessible by ladder, but Broulet & Brothers built the sturdy freight elevator and designed it to look like a natural part of the abandoned factory. The control panel has a hidden keypad to input the access codes for the lower rooms. It can be shut off by the supercomputer for up to five or six minutes. Each floor below is sealed shut by a heavy duty sliding door with a hydraulic clamp.

A large two-floor tall chamber just below the factory's boiler room was presumably once the buffer floor of Renault's secret post-war bunker. It is now lined with a patchwork of metal plating and dimly lit in a vaguely green shade. The upper half of the chamber is lined with a complex network of water pipes running from the water heater in the boiler room to other areas of the factory, and the crawl space behind the water heater leads onto a catwalk just below the pipes with a ladder built into the wall down to the floor and a hatch to go further down. A metal circular basket-like structure is firmly connected to the catwalk from below and supported on two walls on either side, and a large mechanical arm hangs from the structure and uses it as a track to circle around the room. The bottom end of the arm holds the computer interface, which consists of one large monitor with a CD drive and three smaller angled side monitors on the sides and top, as well as a keyboard below.

A large holographic projector sits in the center of the floor, nested inside a segmented hemisphere, collectively with the projector itself known as the Holomap, that is orbited by a circular track on which trails an old repurposed yellow dentist's chair. The chair, like the mecanical arm holding the interface, can be revolved around the lab floor to the convenince of the user. The Holomap is in the middle of a circular space of paneling that covers the complex wiring below, with cables trailing out and into corner panels on the walls. On one side of the room is the hydraulic-locked door to the elevator, while on the other side is the floor hatch directly below the boiler room crawl space that goes straight down into the Scanner Floor.