From the Super Mario Wiki
Hyrule Castle is a lengthy stage in Super Smash Bros. based off The Legend of Zelda series. In the single-player mode, Hyrule Castle is the first stage the player battles on. During gameplay, a whirlwind will occasionally appear, about every 30 seconds, that will blow the character that gets caught in it upwards, usually resulting in being knocked out of the level. The castle also has a little shack at the far right end of the stage, which may act as an additional platform.