World 1-Castle (New Super Mario Bros. Wii)

 is the first castle level in New Super Mario Bros. Wii and the final level of World 1. It is unlocked by completing either World 1-5 or World 1-6. The level introduces Thwomps and Big Thwomps, which make their first and only appearances in the game here. Larry Koopa awaits the players at the end of the level; defeating him allows the players to advance to World 2. This is the first level to feature the castle theme.

Layout
This castle is filled with lava and features many cogs. Mario and co. must hide in the holes in the gears to avoid being crushed. If the players ride one of the gears upward, they can find a small area with coins, a Propeller Mushroom, and two 1-Up Mushrooms. After the midway point, multiple Thwomps and Big Thwomps are encountered. A Red Ring is found before a row of Thwomps. Larry Koopa is fought again at the end of the level. In this fight, Magikoopa animates five platforms, causing them to start moving up and down. The first, third, and fifth go the opposite way of the second and fourth. As in the tower battle, it takes three hits to defeat Larry.

Star Coins

 * Star Coin 1: The first Star Coin is floating above the fourth gear. Mario and co. can either jump to it from that gear or use the third gear to access a hidden platform and fall to it.
 * Star Coin 2: The second Star Coin is located under the first Big Thwomp, blocked off by blocks. Mario and co. should make the Thwomp fall to break the blocks, then collect the now-liberated Star Coin while the Thwomp is ascending.
 * Star Coin 3: At the final gear, instead of getting off and heading toward Larry's door, Mario and co. should stay on the gear until they can access the green Warp Pipe directly below. This leads to a small area with a P Switch, a row of coins over lava, and a row of Brick Blocks. Mario and co. must then activate the P Switch to make the rows switch places, then use the new rows to reach the third Star Coin high up to the right before the P Switch's effects wear off.