City of the Saved
From TARDIS Index File, the free Doctor Who reference.
The City of the Saved was a metropolis that size of a spiral galaxy located between the end of the Universe and the beginning of the next.
It was inhabited by every single Human, Near-Human or humanoid who was ever resurrected after death in an immortal, invulnerable body. Only Human beings were resurrected and those that were partially Human were treated as second class citizens known as "collaterals" who were also forbidden from holding public office.
Whenever history was rewritten by the War between the Great Houses and their Enemy then the City's history was retroactively rewritten with it to include any newHuman beings or versions of them that were brought into existence by the change. This meant that the population of the City was much larger than anyone else on the outside suspected.
It was constructed by two Secret Architects who were a mystery but many believed the City itself was a goddess that was worshipped under the name of Civitata. (FP: Of the City of the Saved...)
