Dungeon of Doom is the 7th fortress in the Mushroom Kingdom. It is based off the dungeons from Super Mario Bros. 3 and Yoshi's Island. The initial area is influenced by a dungeon from Super Mario Bros. 3 where the player must negotiate through one long hallway and switch between its different halves through the doorways. After that is another hallway filled with false floors and some fence climbing. Boom Boom serves as the end boss
Originally, the level was not based upon Yoshi's Island, but rather, a typical fortress. As Shodian created the level, someone on the forums suggested that it be reskinned into a Yoshi's Island-esque fortress, so that it would have a theme, contrasting its original design.