Lunar Tower

The Lunar Tower is a supposedly hidden area in the Fourth Floor of Princess Peach's Castle. It is accessed by following a staircase similar to the one leading to the second floor.

Appearance
The area resembles a very tall tower, which can be inferred by the skybox having clouds on both the bottom and top of it. The tower is shaped like a octagon and most of it's floor is covered with grass and concrete. The roof of the tower is shaped like a cone and is textured like the castle's roof. Depending on if the player has beaten Red Moon Monastery already or not, the ceiling of the tower will depict either a red crescent moon with a dark background or a white crescent moon with a blue background.

The area also contains an unique statue of a crescent moon in the middle of it, the text on the plaque seems to be different than the text on the Eternal Star. There are various theories about what the text could mean, however none of these can be verified because of it's low resolution. Some reports even propose that the text is changing every time the player is accessing the area, however these claims are dubious at best.

Red Moon Monastery
The area apparently contains a way to access Red Moon Monastery, which is supposedly related to the internal clock anomaly. Before beating Red Moon Monastery, every night will result in the screen having a red tint in and around the castle and the moon always resembles a blood moon. Another notable quirk is that Red Moon Monastery can only be accessed at night. By looking directly at the red crescent moon on the ceiling of the tower, the player will be teleported to Red Moon Monastery. After beating the level, the player will not be able to access Red Moon Monastery anymore as the tower's ceiling has changed and now depicts a white crescent moon with a blue background. The nights now feature a normal full moon and the red tint is replaced by a light blue tint.

The Lunar Tower features a unique soundtrack, which sounds foreboding and invokes feelings of impending doom. It can be listened to here.

"Eternal Moon" plaque interpretations

 * 1) There are reports claiming that the plaque sometimes depicts binary or morse code. These reports haven't followed up with their translations yet, so these claims should be taken with a grain of salt.
 * 2) "Beware of the - Eternal Moon"
 * 3) "Embrace the - Eternal Moon"
 * 4) "Many layers to - What is real"
 * 5) "When the lights change - The form remains"
 * 6) "The cosmos decides - What you see"
 * 7) "[Seemingly random letters] - Red He [followed by 5 undecipherable letters]"
 * 8) "[Undecipherable letters] - Powerless"