World 4-1 (New Super Mario Bros. 2)
From the Super Mario Wiki
The player begins in front of a slope where several Mini Goombas roam about. Following that, there is an Icy Spike Ball, acting like a regular Spike Ball. They deflect upon hitting a wall or gravity pulls them down on a slope. Above that is a ? Block containing a Super Leaf. More Mini Goombas and a larger version of the ice boulder appear, followed by a rope on the ceiling to help Mario cross the area with Icy Spike Balls below. Following that is a red Koopa Troopa, followed by another Icy Spike Ball rolling up and down slopes on the ground. A Gold Flower can be found in a Brick Block before the Checkpoint Flag by using a Koopa Shell. A ? Block containing a Super Leaf can then be found, followed by some Mini Goombas and Icy Spike Balls. Going up the structure, the ground switches to ice and thus is slippery. Reaching the top, the player can find a Gold Ring and some Koopa Troopas where he could earn coins by sliding down the slope. At the end of the slope, an Icy Spike Ball rolls opposite, so Mario has to duck. Immediately after that is the flagpole.