World B-4

World B-4 is the fourth and final level of World B in Super Mario Bros.: The Lost Levels and the twelfth secret level overall in said game, taking place in a castle.

Layout
The player starts at the top of some stairs that end at a pit of lava with small platforms and pillars. After a pipe with a Piranha Plant, there are two Fire Bars over a pit of lava and a Brick Block with a power-up in a crevice to the left. In the upcoming narrow passage, the player will have to fall onto a moving lift to pass under a wall (while crouching if needed) and jumping back up once on the other side to continue. Next, the player will have to move through an area with large platforms, with Fire Bars and pipes with Piranha Plants alternating between them. The first three are Warp Pipes that lead back to the beginning of the level, though the fourth is a Warp Pipe that leads to a Warp Zone to World D. After the fourth pipe is lava with a Fire Bar over it before the Fake Bowser.

Level statistics

 * Power-ups: 1 (Super Mushroom or Fire Flower)
 * 1-Up Mushrooms: 0
 * Secret areas: 1