X-Men (Earth-16)

The X-Men are a group of people (or a team), who inhabit the Savage Lands. They use this island in the Pacific Ocean as a safe haven for mutants everywhere. They have built a school that is being run by Prof. X, a defense squad just in case of an attack from the outside, and a nice town for all the mutants to train.

Also, in the basement of the school is the training grounds to practice powers in. It is underground so they don't ruin the beauty of the Savage Lands.

Origins
The X-Men was founded by Charles Xavior. He provided a school for people with "special talents". His first students were Bobby Drake, Scott Summers, Hank McCoy, Warren Worthington III, and Jean Grey. The school gradually grew larger in population and the first students eventually became faculty. They weren't just a school though, they were also the team X-Men, fighting to defend those who hate and fear them. Soon after the cold war, the mutants got a very bad rap caused by the brotherhood of Mutants, lead by Magneto. The humans declared war against the mutants.

War
The X-Men went into hiding. Five other non-mutant heroes bought the Xavior School and let them hide in it. The war didn't last long and the X-Men came out of hiding. They weren't allowed to use their powers anymore, a rule made by the President of the United States, so the X-Men quickly fled to the Savage Lands.

After evacuating all the dinosaurs to another dimension, They started rebuilding their schools and a new town for all mutants to stay in.