Stoneslide Tower is the second tower in New Super Mario Bros. U. It features stone platforms that are movable by spinning on wooden screws. After completing this level for the first time, Kamek flies around Peach's Castle and a tornado starts to form around it. This level is unlocked by completing either Perilous Pokey Cave or Fire Snake Cavern, and completing this level unlocks a labyrinth of connected Stone-Eyes on the overworld map that serve as the location for both Goomba and Fire Bro enemy courses. Navigating the enemy courses unlocks Spike's Spouting Sands and Dry Desert Mushrooms.
The level begins with large Screwtop Platforms that can be moved by spinning on a wooden screw, allowing the player to reach a Warp Pipe that leads to the next section. Another screw controls a platform, allowing a ? Block containing a power-up and the platform above to be reached. Two Spike Top are found on a portion of the ground. A screw controls a pair of smaller Screwtop Platforms, along with another platform that crushes a group of Dry Bones blocking the path. More Dry Bones are found, along with a screw that controls two Screwtop Platforms. Three more Spike Tops are found. Another screw is used to control three Screwtop Platforms. On the left wall, there is a Hidden Block that contains a 1-Up Mushroom. The other one on the right contains a coin. These Screwtop Platforms allow access to a Warp Pipe that leads to the Checkpoint Flag. Another screw controls a group of Screwtop Platforms, one of which having a Super Dry Bones on it. A yellow Warp Pipe on the right takes the player to a room with a Roulette Block. A Dry Bones is found, along with Spike Tops on Screwtop Platforms. Following more Screwtop Platforms and Dry Bones, a group of Pipe Cannons is found. The player must use a screw to move Screwtop Platforms out of the way, allowing the Pipe Cannons to be used to reach the boss door. Two Super Dry Bones are found, as well as a Hidden Block containing a Fire Flower on the left.
Through the boss door, there is a boss battle with Boom Boom. Kamek appears before the battle, giving Boom Boom the ability to attack using spin jumps. He is defeated after being jumped on three times.
- Star Coin 1: At the beginning, the player must rotate the screw and use the Screwtop Platform to jump onto a ledge on the left in order to reach the first Star Coin.
- Star Coin 2: The player must rotate the third screw, then run to the left and Wall Jump up in order to collect the second Star Coin.
- Star Coin 3: Above the Checkpoint Flag, the player must rotate the screw next to some quicksand. It causes the Screwtop Platform next to it to rise. The player must run under it and jump along the left wall to discover a hidden warp pipe. Inside, the player must use the screw to move the Screwtop Platform and guide the Grrrols so that they break the Hard Blocks. Then, by carefully avoiding them, the player must go left and grab the third Star Coin.