Orphan 55

Orphan 55 was the name given to Earth in one possible timeline, where it was designated as an orphan planet after nuclear war and global catastrophes rendered it a barren wasteland. In order to survive the radiation and carbon dioxide atmosphere, what remained of humanity evolved into mutants known as Dregs.

Eventually, Kane built the Tranquility Spa on the planet in what used to be Siberia, taking advantage of the open space. The spa was only made accessible via teleport, and concealed the outside world from visitors. The Thirteenth Doctor and Team TARDIS arrived soon before the spa was attacked by Dregs, and uncovered the true nature of the Kane's resort and the planet beyond. (TV: Orphan 55)