Bowser In The Dark World

Bowser in the Dark World is the first Bowser level in Super Mario 64, found by going through the 8-star door in the First Floor of Princess Peach's Castle. The 8-star door leads to a hallway with a Princess Peach painting which warps into a Bowser painting, and a trap door in the hall leads to the level. It is a long, linear level made of concrete and rock platforms. At the end is the first boss fight with Bowser, which unlocks the Castle Basement. There is also a star for collecting 8 red coins.

Trapdoor Sound
There is an unused sound in the files for the trapdoor leading to Bowser in the Dark World opening.