Pipe Land Treasury
From the Super Mario Wiki
In The Adventures of Super Mario Bros. 3 episode Misadventure of Mighty Plumber, Bowser and Mighty Plumber break into it through the Maze, when Mighty Plumber is convinced that Mario and Luigi are trying to steal it, and they have to get all the Coins inside to Castle Koopa.
Once King Koopa gets the money from the vault, he locks Mighty Plumber inside and escapes when a security system consisting of a flood initiated. Mario and Luigi appear and free him, and they are able to stop King Koopa from escaping with all of the coins.