Action Comics #242

While on an experimental rocket, Clark & Lois encounter the alien Brainiac, who plans to shrink & bottle great cities of Earth & use them to repopulate his planet. Superman gets inside Brainiac’s ship when the villain takes Metropolis & there finds a bottle with a Kryptonian city (which in later issues will be named Kandor). He enters the bottle and with the help of a scientist restores the cities of Earth while Brainiac lies in suspended animation for his trip home. Because there is not enough power to restore the Kryptonian city, Superman places it in his Fortress, as Brainiac rockets away.