World 7 (Super Mario Bros. 2)

World 7 is the seventh and final world in the game Super Mario Bros. 2. Taking place high above the clouds and in the sky, this is where Wart resides. At the end of level 7-1, the player fights a green Birdo. In 7-2, the final stage of the game, it takes place in a massive fortress belonging to none other than Wart. This is the longest level in the game, and it features multiple fights against Birdo. Also, it features a fight with Hawkmouth at the end, which comes to life and attacks the player before allowing them to advance to the final room, where Wart is fought. Wart must be defeated by throwing vegetables into his open mouth that come from a vegetable machine in the room. Once defeated, the good inhabitants of Subcon can be freed.

Trivia

 * Unlike most worlds from Super Mario Bros. 2, this one only has 2 levels instead of 3.