The Great Cave Offensive
From the Super Mario Wiki
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The Great Cave Offensive appears as a stage in Super Smash Bros. for Wii U, based on the sub-game from Kirby Super Star and its remake. The stage is set inside a large cavern with every area of The Great Cave Offensive making an appearance, the Sub-Tree at the top, the Crystal area on the right, the Old Tower in the center running front top to bottom, and the Garden on the bottom left. Both this and the Omega version of the map are available in 8-Player Smash.
This is the largest stage in the game, being so big that "Danger Zones" (walls of lava) are on the wall set to automatically K.O. anyone above 100% damage, to speed up gameplay. Treasure chests appear and disappear on the stage throughout the match, which spawn items when attacked. Minecarts appear on the stage that automatically move across the stage after some time, and players can ride upon them to hit other fighters.
The Omega version of the stage is set on a single circular platform, the left half based on the Sub-Tree area and the right being the Crystal area.