World 4-1 (Super Mario Bros.: The Lost Levels)
From the Super Mario Wiki
Moving to the right from their starting position, the player will encounter red Piranha Plants and a Lakitu; there is also a Coin Block in the bottom Brick Block of the upper pillar. In the row of ? Blocks ahead, there is a power-up in the far-right block, followed by a Springboard that can help the player get over a large gap. After the gap is a flight of stairs with a Hidden Block containing a 1-Up Mushroom directly against the back of it. In the next row of ? Blocks, there is a Poison Mushroom in the far-right block, and there is a power-up in the right block in the next group of ? Blocks. Using said ? Blocks as a platform, the player can reach the pipes above, the left of which is a Warp Pipe to an underwater area with Coins, Bloopers, and Buzzy Beetles that will exit out to a pipe near the one that was entered. In the Brick Block above is a Beanstalk that leads to a Coin Heaven, though it will drop the player at the end to the stairs with the hidden 1-Up Mushroom from earlier. After the brick with the Beanstalk is a flight of stairs with a Goomba walking down them, followed by the Goal Pole.