Fortress

Fortresses or Forts are fortified buildings first found in Super Mario Bros.. After reaching the Fortress, Mario or Luigi can advance to the next level.

Super Mario Bros.
In Super Mario Bros., Fortresses are found in the end of all levels (except the Castle levels), and are required in order to go to the next level.

Super Mario Bros. 3
In Super Mario Bros. 3 they are called Mini-Fortresses, and are usually found in the middle of worlds. They are guarded by Boom Booms and must be defeated to gain access to other parts of the world. The challenge of Fortresses generally depends more on traps or obstacles rather than enemies.

Super Mario World
Later, Fortresses reappear in Super Mario World, and are the same as in Super Mario Bros. 3. Now, Fortresses are guarded by Reznors, and didn't appear in the middle of the levels. Most of them are optional.

Forts are in their respectful remade games in Super Mario All-Stars and Super Mario All-Stars + Super Mario World. In other words, the return in Super Mario Bros., Super Mario Bros. 3, and in Super Mario World.

Super Mario World 2: Yoshi's Island
Forts are also boss levels in Super Mario World 2: Yoshi's Island. They act like the mini-boss levels of each world. All of these levels have the word Fort in their name.

New Super Mario Bros.
The Fortresses later return in New Super Mario Bros., and reprise their roles from Super Mario Bros. as allowing Mario or Luigi to continue to the next level. Fortresses also appear to as levels in the middle of the worlds, similar to in Super Mario Bros. 3, but these ones are called Towers, and are more thinner, resembling towers, as their name say. Also, unlike Fortresses from Super Mario Bros. 3, in which the player may have to progress from left to right, these ones feature vertical direction. One appears in the middle of every world, but World 6 and World 8 have two Towers. At the end of every Tower, Bowser Jr. is faced.

Yoshi's Island DS
Forts return in Yoshi's Island DS, with the same role as in ''Super Mario World 2: Yoshi's Island.

New Super Mario Bros. Wii
Fortresses return in New Super Mario Bros. Wii, with the same role as in the prequel. Now they have different color schemes; the normal ones are brown like in the prequel, and the secret ones (the ones found when finding secret exits) are black. The Fortress levels from the prequel also appear, but they now don't resemble towers, instead they look the same as the Fortresses from Super Mario Bros. 3 and Super Mario World, but are still called Towers. Also, now, all the levels have one Tower, with the exception of World 9. Now, the Koopalings are faced in the Towers, instead of Bowser Jr. He is now faced in Airships.

Appearances in Other Media
In the Mario Ice Capades, during the whole show, King Koopa rode a fort that was surprisingly a moving one. A fort also appeared in the background of the show as a prop.

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 at 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.

Gallery
File:Larry_Koopa.jpg|Mario faces Larry Koopa at the World 1-Tower. File:RoyBattle.jpg|Mario and Luigi face Roy Koopa at the World 2-Tower. File:Lemmy_Koopa_NSMWii.PNG|Mario and Luigi face Lemmy Koopa at the World 3-Tower. File:WendyBattleNSMBW.jpg|Mario faces Wendy O. Koopa at the World 4-Tower. File:Mario_vs_Iggy_Koopa.PNG|Mario faces Iggy Koopa at the World 5-Tower. File:Morton_NSMBWii_Tower.jpg|Mario faces Morton Koopa Jr. at the World 6-Tower. File:Ludwigfortressnsmbw.jpg|Mario faces Ludwig von Koopa at the World 7-Tower. File:Kamek_NSMBWii_Tower.jpg|Mario faces Kamek at the World 8-Tower.