The Backrooms.

You find yourself in the normal living earth you live on (Frontrooms) and every year thousands of people go missing without a trace. But secretly in Los Angeles a government private company called "Async" has been finding and hiring people in the area called The Backrooms. You can only get to the Backrooms by nocliping out of reality or getting sent by Async but when you're in there it is all most certain you will never come back. The Backrooms is filled with vast safe and unsafe levels with no entities or flooded with them but everyone starts off in "Level Zero". Level Zero is a never ending and oddly uncanny endless maze with yellow wallpaper, brown moist carpet and white ceiling lights that hum infinity and if your lucky you can find Async headquarters or Async stations. Level Zero has sublevels and a few entities but you can find entrances to other levels of nocliping to other levels