Factory (Super Mario RPG: Legend of the Seven Stars)
From the Super Mario Wiki
The Factory (also known as Smithy Factory) is the gloomy dimension where Smithy and his cohorts resided in Super Mario RPG: Legend of the Seven Stars. The entire factory is filled with Smithy's Machine Made weapons and the assembly lines that carry them. The factory's design greatly resembles the Airships of Super Mario Bros. 3, including the Bolt Lifts sometimes utilized to reach far platforms and the fog that fills the air.
Smithy's Factory also refers to World 7 of the game. This region includes the Factory dimension as well as the gateway to Mario's dimension, in this case, the Smithy Gang-occupied Bowser's Keep and Vista Hill.
After defeating a Machine Made Yaridovich, a Brick Block explodes to open a passage deeper underground. This leads Mario and company directly to a boss battle against Cloaker and Domino and their pet snake (either Mad Adder or Earth Link, depending on which of the bosses is left standing).
The inner part of the factory is seemingly made of all steel. To the right, in each room, Mario can witness the process of a Jabit being manufactured.