World 6-Castle (New Super Mario Bros.)
From the Super Mario Wiki, the Mario encyclopedia
To start, Mario should jump on the stone platforms as they pop out of the walls, avoiding the lava. The first Star Coin can be obtained by throwing a Shell at it. The second Star Coin is found halfway into the stage, on a moving stone platform. After dodging some fireballs, the player will reach the midway point. Mario should Wall Jump to the top set of platform. Then, the player should see a Koopa Troopa and two stone walls to the right. If Mario runs and jumps off the Koopa Troopa, and goes right at the moment the wall is at its lowest point, Mario should be able to go over the wall. Mario should go right to reach the last Star Coin. Alternatively the player could use the Mini Mushroom and jump to it. After going through a door, the player should time their jumps correctly, in order to reach the double doors. Past the door is World 6's boss, Monty Tank. The battle takes place outside the castle. To defeat him, Mario must jump on his head three times whenever he comes out of the tank, or throw Bob-ombs at him. Each time he is hit, however, another cannon will appear on the tank. After beating Monty Tank, Mario is able to go to the final World, World 8.