Super Mario 64/Vanish Cap Under the Moat
Location: This course can be found in the moat. You must drain it first. After defeating Bowser in the Dark World, you can open the key to the door of the basement. Go in to the basement of the castle. Follow the circular hall, and go through the door. Follow the wall on the right until you hit a wooden door. Go through the underwater hall, and you will find a room with two pillars. Ground-pound the pillars and the water will drain. Go out the newly exposed door, outside the castle, go right, and you will find a hole in the ground by the waterfall. The course lies through there. That's the blue switch!
Description: A short course with a long hill and a bunch of rotating lifts over a bottomless pit.
Finding the Switch
Once you enter the course, you will be given a Vanish Cap, however, it is useless on the slide slope. Go down the slope, ride the platforms, and there's the blue switch. Now you can become Vanish Mario, and slip through cages and ice without even having to try!
8 Red Coins
The first four red coins are found on the slope, along with the 1-ups, so try to slide carefully onto the platforms. If this is too difficult, you can crawl on the slope without falling off. If you fall off, you will exit from a gaping hole near the waterfall without losing a life. The other three coins are found on or near the rotating elevators, so jump carefully. The last one is at the end, next to the blue ! Switch box which you can press to activate the Vanish Caps. Use the Vanish Cap get the coin and go through the cage to get the star. In the DS version, you can use either Mario or Wario to jump on the rotating elevators, though it is generally easier to control Mario than Wario. Wario can use Luigi's Cap and use the power flower to turn invisible and go through the cage to get the star.