World 4-6 (Super Mario Bros. 3)
From the Super Mario Wiki, the Mario encyclopedia
Unique to World 4-6 are two Magic Doors placed near the beginning and middle of the level that change the sizes of enemies and the location of some items. The player starts on the "giant" side of the level.
The player starts on a plain with a Colossal Koopa Paratroopa coming toward them, followed by a ring of Brick Blocks with Giant Koopas around and in it. If playing on the giant side of the level, the player can find a 1-Up Mushroom in one of the blocks, or a Starman if playing on the small side. Across the gap is a pipe with a Piranha Plant or a Piranhacus Giganticus in it, followed by some Semisolid Platforms, within which the first Magic Door can be found. Above these platforms are some clouds with coins above them the player has to fly with a Super Leaf to reach. Across a gap afterward is a ? Block containing a power-up on the giant side, or a single coin on the small side. Next is a formation of Wood and Brick Blocks, with one of the bouncing Wood Blocks containing a Starman, and one of the Brick Blocks containing ten coins if on the giant side. Afterward are two pipes with a Koopa Troopa/Giant Koopa between them where three Hidden Blocks can be found next to the pipe on the right, with one of the blocks containing a 1-Up Mushroom on the giant side of the level. Following the pipes are more Semisolid Platforms with another Magic Door, then a path of floating Brick Blocks with Koopa Troopas/Giant Koopas walking along them that will help the player across the large gap ahead. Afterward is the goal, with one more Koopa Paratroopa/Colossal Koopa Paratroopa before it.