The Backrooms are a fictional, extradimensional space that's part of internet folklore and the liminal space aesthetic:
Origin
The Backrooms started as a 4chan thread in 2019.
Description
The Backrooms are said to be an endless labyrinth of empty office spaces with flickering yellow lights, stale carpet, and a damp smell. They're also home to shadowy monsters.
Access
To enter the Backrooms, one must "no-clip" out of reality, similar to shifting through a glitchy video game wall.
Games
There are several games based on the Backrooms, including:
The Backrooms: A Steam game developed and published by Ionized Games.
Escape the Backrooms: A Steam game where up to four players explore the Backrooms and must all find the exit alive.
The Backrooms: 1998: A first-person, found footage survival horror game where a teenager accidentally falls into the Backrooms in 1998.