This article is about the outer cases of virtual worlds. For the song, see Virtual World.
Virtual world shells are typically spherical, with trapezoidal onyx-colored panels surrounding everything except the south pole. In Code Lyoko: Quest for Infinity and Code Lyoko: Fall of X.A.N.A., they are a silver grey color.
The shells tend to be very visible within the Digital Sea, but invisible from the inside of the virtual world.
Though a virtual world is only present while the computer in question is active, as shown in "Common Interest", the shell is present regardless of if the computer in question is active. This was shown in "X.A.N.A. 2.0". When the supercomputer holding the virtual world is destroyed, then the shell explodes.
The Cortex's shell's panels are extruded columns of various length, much like the towers throughout the Digital Sea.
At the south pole, an L-shaped flood gate can be found. This consists of several interconnected spheres and tubes, with an entrance at the bottom front. This entrance is sealed by spoked panels, with a circular panel on the front. This circular panel usually has the Eye of X.A.N.A. on Replikas. It does not on Lyoko. On the Cortex, there's more panels than normal.
The circular panel acts as a sort of lock. To access the lock on these gates, Aelita uses a device on the Skidbladnir that links up to the supercomputer so Jeremie can crack the code to get it open. The gate is also used for gathering info from the Network. William also uses the gate to get in and out of Lyoko or a Replika. Lyoko's gate has been used a few times by Waldo Schaeffer as well.
These floodgates are also called "Network Access Gates".