Vanish Cap Under the Moat (called Vanish Cap Switch Course in the message that appears when first entering the course) is a secret course in Super Mario 64 that is accessed through the moat outside the castle, after the water has been drained. To do so, Mario must ground-pound the two pillars in the basement, then go out to the newly-exposed door. He will find a hole in the drained moat near the waterfall that will wrap him to the course. It consists of a massive slope at the start, 8 Red Coins, several moving platforms, and the switch that activates the Vanish Cap when pressed on. The Switch is located at the end of the level. If the player falls off, the player will exit from a hole near the moat and not die.
In Super Mario 64 DS, the course was retitled The Secret Under the Moat and the Blue ! Switch was removed. Also, a Black Brick Block (in a rectangular shape containing three Coins) covered the entrance the to the course, requiring only Wario's strength to enter. This is one of the only three secret levels in the game that only one certain character can access. The others are Bowser in the Sky for Mario and Chief Chilly Challenge for Luigi. Also, if the player falls off, the Bricks will respawn.
There are two Power Stars in this level, with one being exclusive to the DS version.
Star 1: 8 Red Coins
The first four Coins are located on the slide ledges of the start, while the other four are located on the moving platforms along the path to the ! Switch. After collecting all the Red Coins and pressing the Switch, Mario will have to grab a Vanish Cap and go through the cage to collect the Star. In the cage, there is a small square hole. If Mario is not careful, he will fall off.
In the DS version, the player can use either Mario or Wario to collect the Red Coins on the slide or moving platforms (though controlling Mario is generally easier). By using Luigi's Cap, Wario can use a Power Flower, in place of the Vanish Cap, and go through the cage to get the Star.
Star 2: Balloon Mario Switch Star (DS only)
In the DS version is a new area added across the chasm at the bottom of the slide. By turning into Mario, Wario can use a Power Flower to float to the new area. By activating the Star Switch on the platform, the Power Star will appear in the Star Sphere above. Wario can reach it by either floating upwards to it or by using wall-kicks.