Bowser's Castle is a location found in the game, A Koopa's Revenge. It is the first
world that Koopa passes in the game and is where the adventure truly begins. On the map, it is situated at the south-west corner. The setting of this world is fortress-themed. Inside is filled with enemies and obstacles such as Yoshis, Toads, Birdies and the lava. Once Koopa has conquered Bowser's Castle, he then proceeds to Mushroom Forest. The boss of this area is Wario.
This area contains a total of three levels, excluding the Training Level, which is optional. Bowser's Castle 3 contains the area's boss.
- The music that plays in Bowser's Castle is a remix of the theme when fighting a Birdo or a boss in Super Mario Bros 2/Super Mario All Stars/Super Mario Advance
- Bowser's Castle 3 has a secret pipe hidden with the level which leads to the Pipe Passage.
- The starting room of this level is also the start of Castle Mario