World 6-2 (Super Mario Bros. 3)
From the Super Mario Wiki
This is an autoscrolling level, the progress of the player relies heavily on the moving cloud platforms. Mario starts on a small platform made of Hard Blocks, followed by two small slippery platforms, one of them with an Ice Block and a ? Block containing a power-up. Shortly after this, the player must use the cloud platforms to jump over a column of Brick Blocks blocking the path, then a Koopa Troopa, more Brick Blocks and a very high column made of Hard Blocks, which requires the cloud platforms to pass over it. Afterwards, there are two Ice Blocks and a Coin Block, alongside another Koopa Troopa, followed by more Hard Block platforms, a Brick Block with a 1-Up Mushroom and a Warp Pipe leading to the goal.
In the GBA remake, shortly before the goal, there is a Hidden Block that helps the player reach new ice platforms and two more 1-Up Mushrooms.