World 4-B is the second secret level of World 4 in New Super Mario Bros. 2. To unlock this level the player has to locate the secret exit in World 4-.
Mario begins on snow-covered land in front of a large wall and a blue Warp Pipe, taking him underground. He first drops onto several Ice Donut Blocks with several coins below. The floors are made of ice and thus are slippery. Amps are common in this level and many can be found following circular tracks. A ? Block with a Super Leaf can be found here, followed by a multi-coin Brick Block. More Amps follow. A lone Koopa Troopa can then be found on a platform with a single ? Block containing another Super Leaf. A Red Ring can then be found along with Ice Donut Blocks and more Amps. Immediately after is the Checkpoint Flag. A gentle ice slope can be found with several Koopas on it, followed by more Amps. Several blue pipes can be found, followed by one more set of circling Amps and the third Star Coin. This is followed by the pipe back to the overworld. In the last area of snow-covered floor, two rectangular Ice Donut Blocks can be found and finally the Goal Pole follows.
Completing this level unlocks a Warp Pipe to World 4-, skipping everything in between World 4-Ghost House and World 4-Castle.
- Star Coin 1: This Star Coin can be found in the area with the third set of circling Amps early in the level. To obtain it unharmed, Mario will have to go to the hole on the other side and follow the direction of the Amps.
- Star Coin 2: The Star Coin can be seen enclosed in an ice platform after the checkpoint. However, it cannot be reached directly. To obtain it, Mario has to backtrack until the player sees a column of Brick Blocks next to a set of three blue pipes. Mario now has to ground pound the Brick Blocks until he reaches the bottom and slide down the tunnel to underneath the Star Coin. Mario has to avoid the circling Amps to reach it.
- Star Coin 3: The Star Coin can be easily seen below two rectangular Ice Donut Blocks located along the track of a circling Amp. Mario has to stand on one of the Donut Blocks and wait until it drops past the Star Coin. Then Mario has to quickly jump off. This requires timing due to the Amps circling the Donut Blocks. Mario can even use a Koopa Troopa to get the coin from a safe spot.