Bowser Jr. has built not one, but two towers in this World, and for this tower he makes liberal use of conveyor belts. In a mainly vertical level, these moving belts can easily transport you off ledges, making you lose progress. Spikes lining the walls and floors also serve as dangerous obstacles, and some of the belts are built to push you into them. Even after overcoming all of these hazards, you better remain vigilant during your next rematch with Bowser Jr.
Watch out for the Dry Bones above you as you start the level, as it will be dropped near you by the conveyor belt. The first three belts move you to the left, so you must run right to stay on them or fall back down. Jump from the top belt to the higher one on the left. The conveyor belts here will move you toward the spikes, so be careful when running on them. Jump on to the slightly raised belt, then jump up to the stone platform on the right.
A Buzzy Beetle above you will come out of its shell but struggle to run against the belt beside it. Knock the Buzzy Beetle into its shell and kick it off to the platform on the right to make it hit a 10-coin block repeatedly. Go left and jump on to the two short conveyor belts, then on to the next long belt above. Jump to the next conveyor belt on the left wall, then jump to the belts to the right. Run along the belt, jumping over the spikes on the ground, until you reach the first Star Coin. After that, use the nearest belts to get on the stone platform with the Dry Bones.
From the stone platform, jump to the belt on the left, then to the stone ledge to trigger the checkpoint flag. Jump to the conveyor stairway to your right. Watch out for the Dry Bones that walk along the conveyor belts, especially the large one. Get to the top of the conveyor stairway and jump to the stone ledge. There are two cannon pipes here, the left one sends you in an arc to collect some coins but drops you back on the belts, while the right one shoots you upward.
Launch yourself upward, then move to the left a bit so you land on a platform with a belt moving below a large structure with Spike Tops crawling on them. If you're not small or tiny Mario, duck into the small gap to be carried into the narrow tunnel. Stop crouching when you get to two brick blocks above you to break the brick blocks. Jump up to get the second Star Coin, then hop up again to progress. Jump to the conveyor belts above, then jump to the left and go up the steps.
At the top is a cannon pipe, but you don't want to use it quite yet. Instead, jump to the right and grab on to the rope. Climb right along the rope to get the third Star Coin, then drop straight down and crouch to safely move between the spikes. Jump on to the ledge and hop over the thin platform, then go left to reach the double doors. Go into it for your second fight in this World against Bowser Jr.
Boss: Bowser Jr.
Bowser Jr.'s arena has a similar design as the one in the previous tower, but instead of a bed of spikes, you're fighting above a pool of lava. Falling in is instant death, and you even have to watch out for the Podoboos that shoot out of either side of the dangling platform. Bowser Jr. will also switch to his shell-throwing strategy, meaning it is harder to damage him. Once again, knock the shells he tosses back at him and followup with a stomp, or just throw enough fireballs at the guy to defeat him.
Unused Secret exit from the World 6 Tower 2 This secret exit is the same as that of World 1, but it unlocks the unused cannon of World 6 through an unused area just at the beginning entered from a blue pipe that leads to the secret exit and unlocks the cannon.
- Midway up the tower, you should see some conveyor belts with upward-pointing spikes between them. Go right along the belts to reach the Star Coin.
- As big Mario or higher, crouch on the conveyor belt below the platform with Spike Tops. Let it move you to the brick blocks, then stop crouching. You will break the blocks, letting you jump up and collect the Star Coin.
- Jump to the rope near the boss door and move to the right until you touch the Star Coin.