Jump through the stairs.....

Description
This is a time-saving glitch in Super Mario 64. First, go inside the castle. Go upstairs to the spiral staircase leading to the second floor. (the area with Wet-Dry World, the mirror room, etc.) Go to the second-to-last white square in the top left corner (before you go up the stairs). Do a double jump and you should go through the ceiling! It will not show Mario, so you need to adjust the camera view first. (Also, the color of the square may be wrong. If so, try another one.)

Credit
This glitch was discovered by an anonymous... person.