World 1-Castle (NSMB)

World 1-Castle is the castle of the first world of New Super Mario Bros. It is the location of the game's first major boss fight.

Overview
The majority of the level consists of walking on tightropes over lava. Along the way, Mario encounters Podoboos and Dry Bones. There are also several platforms that move up and down, some of which sink into the lava. Eventually, Mario comes across safe ground. However, it is below a ceiling of spikes that slowly comes down to the ground. Mario must jump to in-between gaps before he is crushed, and then get through a second lava-filled area before making it to the boss door.

Boss Fight
Bowser is, surprisingly, the boss of the first world. The fight is very similar to the ones from Super Mario Bros; the fight takes place on a small bridge above a pit of lava, with a Skull Switch at one end. Mario must get either under or over the Koopa King and hit the switch, which will collapse the bridge. After the Koopa King's defeat, he is reduced to a skeleton, and is not seen again until World 8.