Towers are a type of level featured only in the New Super Mario Bros. sub-series, within every installment, the first being New Super Mario Bros.. Towers take the role of fortresses from Super Mario Bros. 3 and Super Mario World, as they are generally found in the middle of a world and include a boss to fight at the end. Later on, at the end of a world is another boss fight in a castle, where either the same boss or a different one is fought, depending on the game.
While Towers are made up of gray bricks like their Fortress counterparts from Super Mario Bros. 3 and Super Mario World, the main difference that Towers have with their design is that they are tall vertical structures. As such, Tower levels are progressed through vertically, whereas several Fortresses and Castles have a horizontal layout. A special type of tower is found in Sky Land of Super Mario Brothers 3, where it is required to access the sky portion. This has a similar layout to the Fortresses seen in the game, albeit with a shorter stage.
In New Super Mario Bros., Bowser Jr. is fought at the end of each Tower. In New Super Mario Bros. Wii, one of the Koopalings are fought, after which they retreat to a castle accessed later on within the same world. Every Tower in New Super Mario Bros. 2 features a battle against a number Reznors at the end, like Fortresses in Super Mario World. New Super Mario Bros. U is instead like Super Mario Bros. 3 in the sense that most feature a boss fight against Boom Boom.
