World 5-1 (Super Mario Bros. 3)
From the Super Mario Wiki
The player starts in an area with a single Buster Beetle, some Brick Blocks, a Wood Block containing a power-up, and a Chain Chomp. If the player has a Magic Wing, or is powered-up with a Super Leaf or a Tanooki Suit, they can fly to a Warp Pipe leading to a secret area with a chest containing a Music Box, which can be accessed by crouching and flying to a small gap on the right or running across while small, and another Warp Pipe that leads the player to an area below the main level with four 1-Up Mushrooms. Above there are three Brick Blocks, one of them with a Switch Block, which makes two numbers (three and four, or two threes in the NES and SNES versions) made of coins appear. After that, there are some Walking Piranhas, another Buster Beetle and two more Chain Chomps, guarding some ? Blocks, one of them holding a Starman. Afterwards, there are more Walking Piranhas and a Para-Goomba, followed by some Brick Blocks and the goal.