Sorry, but since he didn't post there, I couldn't reply there...
Pre-Crisis, Earth-Prime (aka "Our" Earth, the world without real superheroes) served that purpose, while in Morrison's work, we have the Hall of Heroes and the Rock of Eternity that sit at the center of the Orrery of Worlds.
In regards to PSO2, that is what essentially what Xion (and to a lesser extent the Phontoner's failed clones of her) is.
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