I think Kandor is Superman canon. I'm not a comic book expert, but I'm pretty sure that Kandor was a bottled city that Superman rescued from Krypton. But I'm fuzzy on the details...
Depends on what era you are reading the comics. Kandor is indeed a bottled city in most versions. Sometimes it is directly from Krypton, making it a Kryptonian City - usually the capitol, or 2nd city. At one point it was a random city that was being populated by 'special' people from different worlds the whole galaxy over, whom the 'owner' wished to collect. He tried to miniaturise Superman into this Kandor at one point.