"I know there's a place like that, yeah."
Wally scratched his head, baring his teeth as though he found it awkward.
"But we've only heard of it. We know it's the Kryptonians' new homeland, but no outsiders have ever been there. Clark hid it well—or rather, he deliberately kept his people beyond the awareness of other beings."
Here was what happened. Long ago, Brainiac stole a city from Krypton called Kandor.
Everyone knew that green robot's habit: he loved collecting things. Back when his technology was less advanced, he put cities into bottles. Later, he progressed to stuffing entire planets into bottles as exhibits, taking them out to admire whenever he had spare time.
When the Kryptonians still lived on their homeworld, the star in their planetary system was a Red Sun. They had no superpowers at all and simply could not contend with Brainiac.
Yet after a fierce struggle, they still drove off that perverted collector, losing only Kandor.
But then Krypton exploded. Kandor instead found fortune in disaster, becoming the only surviving Kryptonian city. The citizens imprisoned in the bottle became the last batch of Kryptonian Survivors.
After Clark grew up on Earth and clashed with Brainiac, he quickly discovered Kandor inside the bottle. During one operation, he snatched the bottle back from that green bald man.
Superman had always been responsible for protecting and watching over it. For a long time, he could not find a way to restore the city to its original size, so he could only keep it safely in a special laboratory within the Fortress of Solitude.
But as the times changed, and after major events like Flashpoint, Superman finally found a method to restore Kandor and its millions of citizens to their proper size.
Strictly speaking, Superman's mind was merely fast enough.