Hollow Horror Halls

Hollow Horror Halls is one of the secret courses in Super Mario 64, housing two of the castle's secret stars. Commonly depicted as a ghastly labyrinth of corridors, the level was supposedly cut from the final build of Super Mario 64 despite players recollecting this level's existence.

Geography
While Hollow Horror Halls' exact geography is unknown, the level's description remains consistent amongst players who claim they have come across this level. Hollow Horror Halls is an interior level filled with many rooms connected by a maze of hallways, and the objective is to find the five secrets to get the level's main secret star.

Upon entering the level, the player is taunted by an in-game message about how Mario will never escape this "maze of deceit" unless he finds all five secrets. The message is coupled with a ghostly laugh.

The rooms themselves are typically described as barren, with flames being the only consistent thing between rooms. Some rooms would hold Boo paintings where Boos could fly out from and attack the player, with one of the Boo paintings having a secret inside them. Other rooms are said to have large holes within the wooden floor for Mario to jump over.

Some of the rooms are gated off by chained fences, which can be passed through using the Vanish Cap. One of these gated rooms prominently display another star, being Hollow Horror Halls' second secret star.

Existence
Whilst Hollow Horror Halls does not appear in any official rereleases of Super Mario 64, many players have recollected this level's existence as a secret level found in the castle courtyard. Mario would have to ground pound into the floor either in front or behind of the fountain to drop down into Hollow Horror Halls; the location of the entrance appears to vary between stories.

In footage shown off from Spaceworld 1995, a level very close to Hollow Horror Halls in appearance is seen. Players recollect the same brick wall and turqouise carpet in the footage, and assume that the level belongs to Hollow Horror Halls. It could also very well belong to Big Boo's Haunt, or Big Boo's Forest, another course with a similar spooky theme.

Disk Version
Hollow Horror Halls was one of the secret courses set to be turned into a full course in the disk version of Super Mario 64, as stated by an anonymous developer in 2004. The developer failed to acknowledge the level's anomalous nature, leading many to assume that the developer assumed the level was in the original Super Mario 64. Like many other players, the developer says that Hollow Horror Halls is accessible through the castle courtyard, yet the method of getting there is left ambiguous.

Hollow Horror Halls would have supposedly gotten four brand new stars to collect, as well as an extra one for the hundred coin star. Any changes to the level weren't specified by the developer, including any changes to make a hundred coin star possible, however they mentioned a star where Mario would have to defeat all the Boos to awaken a Big Boo.

Theorising
It's possible that with Hollow Horror Halls, many players are mistaking other similar levels for its existence. Most obviously is Big Boo's Haunt, another ghostly themed level that has Mario running around cramped corridors with Boos and is accessed through the castle courtyard. The corroborating accounts by other players could merely be falsifying memories of this level's existence. However, the stark differences with the level's objectives, appearance and method of entry not to mention the consistency between unrelated accounts leaves many skeptical to this theory.

Much like many other levels not found in every player's copy of Super Mario 64, the existence of Hollow Horror Halls is usually attributed to the idea that Super Mario 64 copies are personalised. The secret level is only presented to the player if the supposed A.I. in Super Mario 64's code decides the player is worthy of visiting the level. Many already speculate that the level was removed due to the level possibly being too hard for beginners, and the A.I. could be giving the level to more experienced and explorative players. This theory is entirely under the assumption that the personalisation A.I. does exist.