On the old movie of superman he made his Fortress of Solitude by throwing a piece of kryptonite from his shuttle to earth, to the arctic. Inside there are sunstones that he can put into the Fortress of Solitude to see messages from his father Jor-el and his mother Lara. There's also a place in the Fortress of Solitude where he can give his powers away to be human. On the old superman movie he gave way his powers for a little while be human and stay with lois lane, but he had to get them back to face General Zod, Non and Ursa.
The Fortress is also a place for him to get away from crime fighting and relax. But on Superman Returns it does not show him in the Fortress of Solitude for long is shows him floating above earth waiting to fight crime and save people. In the modern Fortress of Solitude there is a key called the Steel Key that superman uses to get inside the Fortress and keep people out.
The largest room in the Fortress of Solitude is superman's trophy room Superman’s trophy room is full of things from his past adventures. Like the Duplication Gun, the same one that helped people from krypton create bizarro version of them selves to take over krypton. That is why Genral Zod was in-poisoned him create the opposite Superman known as Bizarro. His collection even includes the gun that Brainiac once used to shrink entire cities.
One other thing in superman’s fortress of solitude is the shrunken city of Kandor and the Phantom Zone Projector. The small city of Kandor was once the capital of Krypton. But Brainiac a superhero turned bad, shrunk it to add to his collection. Kandor is one of superman’s most prize possessions in his fortress of solitude. In the superman comics there are different types of fortresses of solitude. Some are found in different places and look different too.
Superman’s fortress of solitude is constructed out of Kryptonian crystalline material known a sunstone. On Superman Returns Lex Luther combined's sunstone and Kryptonite to form an island made out of kryptonite that would eventually turn into to a contray of Kryptonite.
By Jayden.F