Super Mario 64/Big Boo's Haunt

Big Boo's Haunt is Course 4 of Super Mario 64 DS. 15 stars are required to access it. Enter one of the wooden doors on the left or right side of the staircase on the first floor, then follow the Boo down the hallway and into the courtyard. After that, go to the far left corner and defeat the large Boo there, then walk into the cage to enter Big Boo's Haunt.