4 Ludwig's Castle

#4 Ludwig's Castle is the final level of the Twin Bridges in Super Mario World. It can be accessed by completing Cookie Mountain or Butter Bridge 2. By completing this level, the player gains access to Forest of Illusion 1. This level consists of a narrow maze-like corridor, a large room with a spike-lined ceiling, a tall chamber containing many fences with Climbing Koopas, and a boss fight with Ludwig von Koopa at the very top of the castle.

Overview
The first room has several Bony Beetles and Ball 'N' Chains. Mario (or Luigi) must carefully avoid those to get to the next door. There is a Super Mushroom just after the door. Also, there is a secret path that Mario can take. The square block just in front of the door can be jumped through, and the player must jump up a series of ledges to reach a Warp Pipe, which leads to a 1-Up Chamber. In the next room, Mario has to deal with a spike-lined ceiling, which slowly descends to the floor. Mario must hit the ON/OFF Switch from ON to OFF in the middle of the room to make it go back up, and run towards the door on the left while avoiding the Lava Bubbles to avoid getting crushed, since the spike-lined ceiling eventually descends again after it reaches all the way to the top. In the third room, there are fences with many Climbing Koopas, as well as more spikes. Behind the red boss door is Ludwig von Koopa, whom Mario can defeat with either fireballs or three stomps on the head.

Boss battle
After Mario reaches Ludwig's room, Ludwig spits out up to four fireballs. Jumping on him makes him spin in his shell across the floor. After he stops, Ludwig leaps towards Mario. Jumping on him two more times sends him flying into the air, where he explodes. Afterwards, a cutscene plays, where Mario retrieves the imprisoned Yoshi (which is trapped in an egg) and attempts to blow up the castle. However, the detonation causes the castle to rocket into the air, and it crashes into the nearby hill. The hill gets a bandage after that.