Kandor was once the capital of Krypton until it was shrunken and stolen by the supervillain Brainiac, several years before the planet was destroyed. Superman discovered the city in Brainiac's possession when the android came to Earth decades later to harvest more cities (Action Comics #242, July 1958) and rescued it, keeping it in his Fortress of Solitude while looking for a way to restore it to full size. In return, the Kandorians provided the superhero with a place where he was an honored guest who was occasionally invited to participate in matters of local government, various professionals to assist him when asked and even occasionally assisted him in the outside with the Superman Emergency Squad.
Eventually (Superman #338, Aug 1979), Superman was able to restore the population to normal size and they settled on another planet that revolved around a red sun. The Kandorians decided to name their new homeworld Rokyn, which is the Kryptonian word for "gift from God" (Rokyn had first been revealed as existing in the 30th century in Adventure Comics #356, May 1967). Superman constructed a replica of the bottle-sized city to keep as a memento but was surprised when thousands of tiny aliens, fleeing the destruction of their home planet, moved into it (Superman #371, Aug 1982). When told the city's original name was Kandor, the aliens decided to call it that as well. On a trial basis, Superman restored two inhabitants to normal size to introduce them to life on Earth, but discovered that population has a dangerous reaction to the planet's environment which transforms them into mindless, powerful and rampaging beasts who were difficult for Superman to control. As such, Superman decided that for the time being, the New Kandorians would have to remain in the bottled city with a carefully filtered atmosphere until that medical problem was solved
