Tower

Towers are a type of level appearing in New Super Mario Bros.. They are more or less the equivalent of the Fortresses from Super Mario Bros. 3, Super Mario World, and New Super Mario Bros.. Unlike most Fortresses, in which the player may have to progress from left to right or vertically, Towers exclusively feature vertical direction. One appears midway through every world (except for World 6 and World 8, which have two). The challenge of Towers generally depends more on traps and obstacles than enemies.

Towers later return in New Super Mario Bros. Wii. Each world has one (except for World 9), with the first seven towers housing the seven Koopalings, while the last one is home to Kamek.

New Super Mario Bros. Boss Fights
At the end of every tower, there is a boss fight with Bowser Jr., who becomes increasingly more difficult as Mario (or Luigi) reaches each Tower. When Jr. is defeated, he gets back up and jumps off-screen (and out of the Tower). Additionally, the first time Jr. is defeated in each tower, a brief cutscene ensues on the map, showing him running with Princess Peach to the Castle of that world.

World 1: The fight is simple, with no obstacles. Bowser Jr. runs at the player to attack. World 2: The fight is a bit harder, as Bowser Jr. now has the ability to jump, and there is quicksand on the arena. World 3: Bowser Jr. can still jump, and the fight is now held on a platform above a pool of water. World 4: Bowser Jr. changes his tactic; this time, he throws Koopa Shells, which need to be jumped on and tossed back. World 5: Bowser Jr. doesn't throw shells, but the fight is on a pillar of ice, which reduces the player's traction, and is held over a bottomless pit. World 6 (1st Tower): The fight is on a see-saw, above a floor of spikes. World 6 (2nd Tower): The fight is on a see-saw, this time above lava, with Bowser Jr. throwing shells. World 7: Bowser Jr. throws shells, and the fight is on moving platforms. World 8 (1st Tower): The fight is like a small obstacle course, with Rocket Engines and moving platforms. Jr. throws shells. World 8 (2nd Tower): The final Tower's fight is on yet another pillar above lava (complete with Podoboos this time), still with shell-throwing added.

New Super Mario Bros. Wii Boss Fights
At the end of each tower, the player faces one of the Koopalings (Kamek in the World 8 tower) in battle. When a Koopaling is defeated, he/she flees to the castle of the same world that he/she is at.

World 1: Larry Koopa is fought at this tower. He basically attacks by releasing light blue fireballs from his wand, and by jumping. World 2: Roy Koopa is fought at this tower. He fights the same way as Larry Koopa, except for that his fireballs are purple, and he'll pound the ground in an attempt to immobilize the player temporarily. World 3: Lemmy Koopa is fought at this tower. He fights by hurling one of his balls at the player, followed by moving to the other side of the arena. At first, he only hurls one ball. After one hit, he'll hurl two. After two hits, he'll hurl three. World 4: Wendy O. Koopa is fought at this tower. Her attack pattern is similar to that of Larry Koopa, but she'll release energy rings from her wand, which will bounce around any walls that they touch. World 5: Iggy Koopa is fought at this tower. Like Larry Koopa, Iggy attacks by jumping, and by releasing fireballs from his wand. However, his fireballs move at a faster speed, and are colored green. Three platforms do move around vertically during the fight. World 6: Morton Koopa Jr. is fought at this tower. He fights in a similar manner as Roy Koopa, but he does make short hops during the process. Strangely, his fireballs are colored purple, just like Roy's, but they move at a faster speed. Two spiked pillars are present during the fight. World 7: Ludwig von Koopa is fought at this tower. Unlike the other Koopalings, Ludwig fights by releasing blue fireballs, which will home in on the player. He'll also jump and perform a set of flutter jumps in an attempt to land on the player. World 8: Kamek is fought at this tower. He first uses his magic to make a bunch of blocks start moving. He'll then teleport from place to place, and release an energy ball, which will turn the blocks into various enemies. After taking two hits, Kamek will release two energy balls before teleporting again. Kamek is not fought again at the World 8 castle; Bowser is that castle's boss.