has been independently broken into at various times by villains Lex Luthor and Brainiac (Action Comics #583 and Superman #423) and the Atomic Skull (DC Comics Presents #35), among others. According to Action Comics #261, Superman first established secret Fortresses in outer space and at the center of the Earth before settling on an Arctic location. Additionally, Superman established an undersea Fortress of Solitude – hollowed out of the side of an undersea cliff – in September 1958. The undersea Fortress, which is reportedly located at the bottom of the Sargasso Sea at 28 degrees North latitude, 50 degrees West longitude, is stocked with numerous exotic ocean relics and is equipped with sophisticated monitoring apparatus to enable Superman to keep abreast of events occurring throughout the seven seas. Superman later abandoned the undersea Fortress and the structure is now used by the mer-people of Atlantis as a showplace and a tourist attraction. The original version of the Fortress of Solitude made its last appearance in the 1986 non-canonical (or "imaginary") story "Whatever Happened to the Man of Tomorrow?". In this story, under constant attacks by returning foes, Superman goes to ground inside the Fortress, taking his closest friends with him for their protection. The villainous android Brainiac soon besieges the Fortress with various allies, surrounding it and the outlying territory with an impenetrable force field to keep Superman's fellow heroes from aiding him. Superman ultimately battles a newly evil Mister Mxyzptlk, who was behind the plot to destroy him. As Superman was forced to destroy Mxyzptlk, breaking his vow against killing, he exposes himself to gold kryptonite to permanently remove his powers and then appears to leave the Fortress to freeze to death in the Arctic cold. Superman is never seen again, although we find out in a "ten years later" wraparound segment set in 1997 that he survives as Jordan Elliot, husband of Lois Lane Elliot, and that they are the parents of toddler Jonathan Elliot, who has super-powers. Post-Crisis versions In John Byrne's 1986 Man of Steel miniseries, which re-wrote various aspects of the Superman mythos, the Clark Kent persona was described as a "Fortress of Solitude", in that it allowed him to live as the ordinary person he saw himself as and leave the world-famous superhero behind. This concept was often invoked in later stories, and one story featured Superman hiding his secret identity from a telepath