Mirror Metropolises of the Multiverse: Floating Fictionopolises

Supertown and Asgard... floating cities filled with fearless friends and fiendish foes of humanity... separated from Earths One and Two respectively by being tucked away in hidden dimensions accessed through boomtubes and bridges. Not bound by traditional physics, its advanced technology coupled with the powers possessed by its legendary citizenry makes it the stuff of legends. Kal-El visited Supertown, meeting its ruler Highfather and other residents of Supertown. Later he along with fellow Justice Leaguers and their allies of Earth-Two, the Justice Society, were brought there by Metron to save the Society's world from Darkseid's plans. Later, or earlier considering your frame of reference, the Justice Society were brought to Asgard to battle Surtur and his plans for conquest that would've led to Earth-Two's destruction. In both instances, the heroes prevailed.