The Cafeteria is a building at Kadic. It is where our heroes, as well as the other kids eat. According to the students it's food is okay, though Odd seems to hate vegetables and fish. The cafeteria is another common location where X.A.N.A. usually attacks Team Lyoko.
In Just in Time, X.A.N.A. tried to collapse the cafeteria (along with the rest of the building) onto those stuck inside.
During Attack of the Zombies, students who weren't infected stayed inside the cafeteria. Since Rosa had fainted, William took care of everyone. Kiwi, however, got inside the building and bit Odd, forcing the others to tie him up or risk being bitten themselves. Aelita and Jeremy were the only ones able to get out; leaving Ulrich inside to help defend the other students.
The Cafeteria appears almost in every season 1-4 episode with Team Lyoko eating either breakfast or lunch there and planning their next movement to attack X.A.N.A.
Interestingly, this is the only building which doesn't fit with Kadic's original model, the Lycée Lakanal secondary public school. In the real world, the cafeteria isn't in this place; in fact, the outdoor view from the cafeteria is an existing building, but way too small to be a refectory (it's a study room).
Rosa Petitjean is the person who manages the cafeteria.