Earth-34 is the home of Savior, last survival of the super-civilization of Mu, who located himself in the city of Cosmoville, which serves as headquarters for the Light Brigade and the most of the super-beings of that universe.
Earth-34 was created by Grant Morrison
Note: Earth-34 was designed to serve as an homage to Kurt Busiek's Astro City.
Post-Flashpoint / Earth-34
It must be noted than most of the characters presented works at least visually as reversed versions from their respective doppelgangers:
It's also known than the adventures of Cosmoville residents are published (in other universes at least) by Spire Comics.