Core Zone is the central passages of Carthage. After someone has entered Carthage from the Arena and gone through the door leading out of the Arena, they have to wait a few seconds for the Core Zone to open. A countdown then starts counting down from 3 minutes or 1 minute and 30 seconds. That is the amount of time a person will have to find the key and stop the countdown. If they don't make it to the key in time, the Core Zone will be closed and they will be trapped until someone else enters Carthage and restarts the countdown. If the key is reached in time the Core Zone will open up to where ever the Lyoko warriors are headed to (usually the elevator). The Core Zone is full of dangers and traps. Huge blocks can suddenly smash down on avatars and devirtualize them. Lasers protect some rooms within the Core Zone. Monsters, like Creepers, usually guard the Core Zone, although Mantas have appeared within the core zone in episodes Franz Hopper and The Key. It was thought that the time limit was actually 2 minutes 30, as in Uncharted Territory, the Core Zone started to close when the timer hit 30 seconds.
New Core Zone
When Carthage was recreated at the beginning of Season 4, the Core Zone was a little bit different from before. The old key system had been removed for practical reasons, so now any visitor to Carthage has direct access to the elevators and the Celestrial Dome. The Core Zone doesn't seem to reconfigure as much as it did before. The Core Zone now also houses the Skidbladnir in a hangar specially programmed for this task. This hangar appears to be darker then the rest of the Core Zone, and can be accessed from either the access elevator or the North Pole in the Celestrial Dome.
Core Zone Access Hall
The Core Zone Access Hall is a passage way that leads from the Arena to the Core Zone. The hallway always has a different construction which shows that it is a very unique part of Carthage, two of its known shapes are the form of a normal passage way but opened like millions of gates, and the second starts like the first but then twist around into a circular corridor. It opens like, as said before millions of gates, and ifs someone hits the Key in time, the countdown will stop and the gates will start closing and if someone doesn't make it to the Arena in time, they get squished. Yumi and Odd are the only ones who have gotten devirtualized by not reaching the Arena in time (though they did get close).