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 empty space. The spa was only accessible via teleportation and concealed the outside world. The Thirteenth Doctor and Team TARDIS arrived as the spa was under attack by Dregs, and revealed the true nature of the resort and the planet. (TV: Orphan 55)