Bowser in the Dark World
Bowser in the Dark World is the first Bowser level in Super Mario 64. It is a challenging puzzle-like world with many traps and enemies that are nearly guaranteed to surprise the player. The trapdoor entrance is behind the star door in the main floor. Eight Power Stars (twelve in the DS remake) are needed to open this door.
Red Coins are difficult to obtain in this level due to the fact that there are many gaps in the course, but simply getting to the end of the course is particularly easy. In Super Mario 64 DS, a Switch Star was added to the level.
While fighting Bowser, Mario must grab him by his tail, twirl him around to build up momenum, and then throw him into a mine. Upon doing so, he will admit defeat and disappear, leaving Mario with the key to the castle's basement.
Music
The stage music is the same as in Bowser in the Fire Sea and Bowser in the Sky, with "Koopa's Road" being used for the course (but not while fighting Bowser).