World 2-3 (Super Mario Bros.: The Lost Levels)
From the Super Mario Wiki
Throughout the level, many Cheep Cheeps will be jumping up from the abyss below and falling back down. The level is made up of several broken up platforms, varying in sizes. Several Koopa Troopas and Koopa Paratroopas are also placed on the platforms, along with one Blooper near the center of the level. In the area with the ? Blocks, the top-left block holds a power-up. After the second set of tall, tree-like platforms is the Goal Pole.