Roy's Conveyor Castle

Roy's Conveyor Castle, or  is the castle of Rock-Candy Mines in New Super Mario Bros. U. It is unlocked when Shifting-Floor Cave is completed and its own completion opens the path to Meringue Clouds and Land of the Flying Blocks. Additionally, the course can be entered via a ! Switch bridge to the back door of the castle. The boss of this stage is Roy Koopa.

Layout
The level begins near a pit of lava. An Iron Block falls from a Conveyor Belt, acting as a platform in the lava. The player can climb the Conveyor Belts and go left to find a Hidden Block containing a 1-Up Mushroom. A Dry Bones is found, and more Iron Blocks fall from the Conveyor Belts above. A Bony Beetle is found, followed by a section where Iron Blocks infinitely drop from Conveyor Belts. Another Bony Beetle is encountered, and Iron Blocks are used to move across a portion of lava. Towards the end is a Brick Block that contains a 1-Up Mushroom. A Dry Bones is found, along with a Red Ring and more Iron Blocks. The Checkpoint Flag is then found. Lava Bubbles are found jumping out of some lava pits. A ? Switch is found, and when it is hit, Iron Blocks with Dry Bones on them fall on top of the surface of the lava, allowing a platform at the end of the section to be reached. The boss door can then be found.

The boss door leads to an area with a cannon, which launches the player to Roy Koopa's airship. Roy attacks by shooting Bullet Bills from his Bill Blaster while jumping between horizontally-moving platforms in the area. Occasionally, he launches Missile Bills. After being jumped on three times, Roy is defeated.

Star Coins

 * Star Coin 1: In order to get the first Star Coin, the player must allow the first Iron Block to fall on the surface of the lava and quickly dash towards the Star Coin.
 * Star Coin 2: While floating on an Iron Block in the middle of the level, the player must wall jump to a hidden Warp Pipe which leads to a hidden room. After entering the hidden room, the player must act quickly by dashing to the second Star Coin and back before an Iron Block falls.
 * Star Coin 3: Access to the third Star Coin requires the secret entrance into the back of this castle on the world map. Next, Mario must step on a ? Switch in order to cause a bunch of Iron Blocks to fall overhead. After that, Mario can now walk on top of the Iron Blocks and get the third Star Coin before the last Iron Block falls and blocks the path to the Star Coin.

Second entrance
The second entrance is automatically unlocked upon completion of Screwtop Tower. However, it will not be accessible under normal circumstances as all paths to the second entrance requires the use of the red Stretch Blocks to the right of Screwtop Tower, which is impossible to have been stretched when Mario is at Screwtop Tower because the south path leads to a blue switch which would have been automatically stepped on and the west path leads to blue Stretch Blocks which must have been used to cross the abyss, and there are no red switches nearby. To get to the second entrance, the player must do one of the following (in addition to completing Screwtop Tower):
 * 1) Complete Waddlewing's Nest and Thrilling Spine Coaster (which requires locating the secret exit in Grinding-Stone Tower). The player can then step on the red switch to the east of Waddlewing's Nest and use the secret path through Thrilling Spine Coaster to reach the now stretched-out red Stretch Blocks and the second entrance. or
 * 2) Find the secret exit in Walking Piranha Plants!. This unlocks a path to a red switch and bypasses the blue switch between Walking Piranha Plants! and Screwtop Tower.

Enemies

 * Dry Bones
 * Bony Beetles
 * Lava Bubbles
 * Bullet Bills (boss battle only)
 * Missile Bills (boss battle only)
 * Boss: Roy Koopa

Trivia

 * This is the only level where the player cannot collect all Star Coins in one run.

Roys Gefahr-am-Fließband-Festung