World 1-Castle (New Super Mario Bros.)

 is the last level and the castle of World 1, and subsequently, the first castle of New Super Mario Bros. The boss here is Bowser.

Layout
The majority of the level consists of walking on tightropes over lava. Along the way, Mario encounters Lava Bubbles and Dry Bones. There are also several platforms that move up and down, some of which sink into the lava. Eventually, Mario comes to a ground platform found below a ceiling of spikes that slowly lower themselves down to the ground. Mario must go to gaps between the spiked ceilings to avoid getting crushed. The first Star Coin can be found in one of the gaps, and Mario must Wall Jump to reach it. Mario then must get through a second lava-filled area. The second Star Coin can be found on a moving platform that sinks into lava. Before making it to the boss door, Mario can jump on the last tightrope to find a hidden Warp Pipe to get to a room with the final Star Coin.

The boss door at the end of the area leads to Bowser, the boss of the first world. The fight is very similar to the ones from Super Mario Bros., as the fight takes place on a small bridge above a pit of lava, with a Skull Switch (which replaces the axe from Super Mario Bros.) at one end. Mario must either go around Bowser and hit the switch, which collapses the bridge, or defeat him with fireballs. After the Bowser is defeated, he falls into the lava and becomes Dry Bowser, and is not seen again until World 8.

Star Coins

 * Star Coin 1 - The first Star Coin is placed near the ceiling. Mario needs to Wall Jump off the moving spiked ceilings to get it.
 * Star Coin 2 - Near the end of the level are two platforms. One of the platforms has the second Star Coin, but Mario needs to wait for the second platform to come up out of the lava to obtain the coin.
 * Star Coin 3 - Right after the second Star Coin is a long stretch of rope. Near the middle of the rope is a Warp Pipe located on the ceiling. Using the rope, Mario should jump to the ceiling and go in the Warp Pipe to obtain the last Star Coin.