Level 78, otherwise known as "Psychological Planet," takes the appearance of a large grassland with an unnatural layout. Hills, mountains, valleys, and fluctuations in the level's elevation are excessively common within the level, making it difficult to traverse without getting lost. Winding asphalt roads stretch across the vast majority of the grassland, typically ending in intersections which open up to numerous other areas with completely identical appearances to the rest. The level is suspended in a "fake," bright blue sky lacking stars and other observable objects. Additionally, Level 78 is set in a perpetual state of daytime, though events that change the sky's appearance frequently happen, giving wanderers the illusion that it is night.
This level is notable for sharing many similarities with the dreamcore aesthetic, a surrealist aesthetic that uses media commonly associated with dreams, daydreams, and sometimes even nightmares. However, it is unknown how Level 78 is able to utilize the dreamcore aesthetic, as reports of the level existing heavily predate the earliest media associated with dreamcore. Some think that the level might have only got its surrealist properties after dreamcore started becoming relevant, or that it is just another of The Backrooms' unexplainable phenomena. Few theorize that the level somehow time traveled and obtained the aesthetics characteristics, though this is near unfathomable as time within Level 78 progresses slower than usual.
While its size is currently undetermined, Level 78 is, unlike most levels of The Backrooms, known to be finite. The level's end has never been reached, though many individuals have reported spotting a point where the grassland abruptly ends. Level 78's shape is undiscovered, though it is thought to be similar to a planet, specifically Earth.