Kelley’s Kandor series stems from the myth of Kandor, Superman’s hometown and the only surviving city on Krypton, which is preserved in a bottle which the comic hero possesses. No definitive representation of Kandor exists, so Kelley explored various representations over the years.
The Chronological Superman 1958:
Brainiac, the conqueror of Colu and collector of alien cities, first appears in Action Comics vol.1 No.242. Among his collection of habitats from thousands of worlds is Kandor, a city ripped wholesale from the surface of Krypton prior to the planet’s destruction. It wouldn’t be the only surviving colony of Krypton to be revealed within the pages of the assorted Superman Family books (a fully populated rogue moon, Xenon, will show up later in the year, and the soon-to-debut Supergirl’s origin depends on an entire city surviving the initial cataclysm).
The argument has been made repeatedly over the last several decades that the preponderance of surviving Kryptonians somehow diminishes Superman’s prestige as the sole survivor of the doomed planet. This seems to come, I think, from a misunderstanding of the term “The Last Son of Krypton,” a subtitle which implies not just mere survival, but inheritance of a legacy. There may be hundreds of thousands – and possibly millions – of surviving Kryptonians scattered throughout space or comfortably residing inside one of the Fortress of Solitude’s cupboards, but there’s still only one of them carrying on the great legacy of the doomed world in actions and deeds celebrated throughout the universe.