Traditionally, the Fortress of Solitude is located in the Arctic, though more recent versions of the Superman comics have placed the Fortress in other locations, including the Antarctic, the Andes and the Amazon rainforest. The general public in Superman's world is at best only vaguely aware of the existence of the Fortress, with its location kept secret from all but Superman's closest friends and allies (such as Lois Lane and Batman). A trademark of the Fortress is that it contains a memorial statue of Jor-El and Lara, Superman's Kryptonian parents, holding a large globe of Krypton. However, although Superman has living quarters at the Fortress, his main residence is still in Metropolis.
The original Silver Age Fortress, first appearing in 1958, was located in the Arctic and built into the side of a steep cliff. The Fortress was accessible through a large gold-colored door with a giant keyhole, which required an enormous key to open it. The arrow-shaped key was so large that only Superman (or another Kryptonian such as Supergirl) could lift it; when not in use, the key sat on a perch outside of the Fortress, where it appeared to be an aircraft path marker.
The Fortress contained an alien zoo, a giant steel diary in which Superman wrote his memoirs (using either his invulnerable finger or heat vision to engrave entries into its pages), a chess-playing robot, specialized exercise equipment, a laboratory where Superman worked on various projects such as developing defenses to Kryptonite, a computer, communications equipment, and rooms dedicated to all of his friends, including one for Clark Kent to fool visitors. As the stories continued, it was revealed that the Fortress was where Superman's robot duplicates were stored. It also contained the Phantom Zone projector, various pieces of alien technology he had acquired on visits to other worlds, and, much like the Batcave, trophies of his past adventures. Indeed, the Batcave and Batman himself made an appearance in the first Fortress story. The Fortress also became the home of the bottle city of Kandor (until it was enlarged), and an apartment in the Fortress was set aside for Supergirl.
A detailed description of the Fortress and its contents forms the background to DC Special Series #26 (1981); Superman and his Incredible Fortress of Solitude, in which Superman minutely inspects the Fortress, suspecting an enemy has planted an Earth-destroying bomb within it. Another noteworthy appearance of this version of the Fortress was in 1985's Superman Annual #11, a story by Alan Moore and Dave Gibbons titled "For the Man Who Has Everything", in which it served as a battleground for Superman, Batman, Robin, and Wonder Woman against the alien would-be overlord Mongul. This story was adapted to animation in the Justice League Unlimited series.
In John Byrne's 1986 Man of Steel miniseries, which rewrote 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, with one story even featuring Superman hiding his secret identity from a telepath behind a door identical to that of the pre-Crisis Fortress. By that time, however, a more physical Fortress had been introduced.
In Action Comics Annual #2 (1989), Superman, on a self-imposed exile to space, was entrusted with a Kryptonian artifact called the Eradicator, created by his ancestor Kem-L. Dedicated to preserving Krypton, this device built a new Fortress in the Antarctic as a precursor to recreating Krypton on Earth. Superman broke the Eradicator's control, but maintained the Fortress as a useful location for emergencies.
The Fortress contained many artifacts from the post-Crisis version of Krypton, most notably a number of robot servitors (one of whom, Kelex, became a trusted confidant) and a battlesuit from the Third Age of Krypton.
This Fortress was cast into the Phantom Zone as a result of a battle between Superman, Lex Luthor, and Dominus, a villain who played with Superman's mind and who was also trapped in the Phantom Zone. It did, however, serve as the template for the next Fortress, built into an extradimensional space accessed through a vast puzzle-globe. The now-mobile Fortress was relocated somewhere in the Andes.
In the DC One Million series (1998), Superman's Fortress of Solitude in the 853rd Century resides within a tesseract located at the center of Earth's sun. By this time, Superman has lived in self-imposed exile within the Fortress for over 15,000 years. During the "For Tomorrow" story arc in 2004-2005 Superman comics, Wonder Woman breached the Fortress in an attempt to confront Superman, causing the Fortress to self-destruct. Superman has since established a new Fortress in an ancient temple on a remote village in the Cordillera Del Condor Mountains, on the border of Ecuador and Peru. This version of the Fortress is visually similar to the earliest "Secret Citadel" from Superman #17.
The current Fortress is home to Krypto and his dog-sitter Ned (the last remaining Superman robot), and contains the current version of Kandor, a portal to the Phantom Zone, Kryptonian and alien artifacts, and holographic images of Jor-El and Lara. The caretaker of the Fortress is Kelex, a Kryptonian robot that is a descendant of the robot that served Jor-El.
In the 2006 limited series Infinite Crisis, several survivors of the pre-Crisis multiverse -- the Earth-Two Superman and Lois Lane, the Earth-Prime Superboy, and Earth Three's Alexander Luthor, Jr. -- set up a base in the ruins of the Antarctic Fortress following their escape from the "paradise dimension" they had been trapped in since the end of Crisis on Infinite Earths. It was then revealed from Power Girl's repressed memories from her life on Earth-Two that her cousin Kal-L had his own version of the Fortress of Solitude similar to his Earth-One counterpart's Fortress.
One Year Later
In the 2006 story arc Up, Up, and Away!, Superman recovered a piece of Kryptonian sunstone, which Lex Luthor had used to awaken an ancient Kryptonian warship. Superman revealed that the sunstone had been sent with him from Krypton, and used it (in Action Comics #840) to construct a new Fortress in the Arctic in the exact same manner as Superman: The Movie (see below). He nevertheless plans to restore the Peruvian Fortress, even if compromised and no longer in a secret location, and plan more Fortresses around the world, reachable to the mass as a public frontend.
Action Comics Annual #10 (2007) revealed that, in the post-IC timeline, the Arctic fortress predated Clark's Superman identity.
All Star Superman
In the out-of-continuity series All Star Superman, the Fortress is once again located in the Arctic. Superman has replaced the giant key with a normal-sized key which is made from dwarf star material and is therefore too dense for any mortal to lift, and has a team of robots working on various projects. The Fortress itself seems to contain the RMS Titanic, the space shuttle Columbia , as well as larger-than-life memorabilia, making it more akin to the Batcave than to more traditional depictions of the Fortress from the Silver Age.
Superman's Fortress of Solitude is a crystalline dome structure in the North Pole. It was here that Superman kept the Bottle City of Kandor, and also where he got sucked into the Phantom Zone. ("The Ghost in the Fortress of Solitude")
In other media
In Superman: The Movie and its sequels, the Fortress is created by a crystal that Jor-El enclosed in Kal-El's spaceship. It leads teenage Clark Kent to an ice field where, after he throws it down, melts into the ice and grows into a huge crystalline building. This feat is similar to other descriptions in science fiction of a nano-assembler device, with what appears to be restructuring of hydrogen and oxygen in the ice and elements in the sea floor under the ice into the crystals the fortress is made of. This Fortress contains numerous "memory crystals" that can be used to access interactive holographic recordings of Jor-El, Lara, and other Kryptonians, and a chamber that uses red sun radiation to strip Kryptonians of their superpowers.
In Richard Donner's cut of Superman II, the Fortress is destroyed by Superman as its existence was revealed to Lex Luthor as well as the police who arrested General Zod, Ursa, and Non. However, Superman then turns back time (ala Superman I), so technically the fortress is completely restored.
In Superman Returns, the Fortress follows the same formula as the earlier movies, but goes into more detail about the crystal origins of the Fortress and Kryptonian architecture. Lex Luthor attempts to use memory crystals he stole from the Fortress to create a new continent. An observation is made (following Superman II leaving the world as it is) that this is not the first time he has been there.
Computer and video games
In the computer game The Death and Return of Superman for SNES, the Fortress of Solitude is shown in one of the cut-screens.
In Superman Returns: The Videogame, It was thought that the Fortress would be accessible. However, it is only shown in one cut-scene. The only locations accesssible in the game are Metropolis, and a small part of Warworld.
Superman: The Animated Series and Justice League Unlimited present a slightly altered version, with the Fortress located in the ocean underneath the Arctic tundra; access was gained by diving into the Arctic water and emerging in an opening inside the Fortress. This version contained an alien zoo housing alien lifeforms saved off The Preserver's ship and some computer equipment, along with a Brainiac information sphere stolen from his hijacked spacecraft just before it was destroyed used by Superman to access information about Krypton.
The Fortress of Solitude is also a major setting for the Justice League Unlimited episode "For the Man Who Has Everything". A fight with the warlord Mongul took place there, after he delivered a parasite capable of hypnosis to Superman and was detected by Batman and Wonder Woman. In this version, the name "Fortress of Solitude" was given by Professor Neil Hamilton in a sarcastically humorous remark while he visited the fortress in one episode.
In Smallville, teenage Clark Kent is often found in his loft in a barn, which Jonathan Kent once called the "Fortress of Solitude" since it is the place where Clark likes to be alone. In the fourth season, Clark began a quest to unite the kryptonian Stones of Power, three artifacts that held all the knowledge of Krypton and the universe. In the fifth season premiere, "Arrival", when the stones were united they formed the Crystal of Knowledge, which then formed the Fortress of Solitude. This Fortress is very similar in appearance to the one seen in the original Superman movies, but much larger in size; it is even constructed in a manner very similar to what was seen in Superman: The Movie.
In the same episode, Chloe Sullivan, having been accidentally transported to the Arctic, found the Fortress and upon entering, was hit with an ice blast caused by Jor-El, who was attempting to educate Clark, and subsequently began to freeze to death. Clark took Chloe to a hospital in the Yukon, indicating that the Yukon is the nearest inhabited place to the Fortress.
The Fortress houses the artificial intelligence of Jor-El, who's essence was transfered from Clark's spaceship, to the Kawatche Caves and into the Fortress. Clark describes Jor-El as adavanced computer programming within the Crystal of Knowledge. It appears, throughout the show, that Jor-El has power over the Fortress and that he controls all of it's capabilities through his own will. Jor-El tells Clark that he was the only one destined to unite the stones and form the Fortress. Jor-El-"For the knowledge of the universe is meant for you only..." The Fortess is used for Clark's training and education so that he can become the Earth's savior.