Morton's Castle is the second castle that Mario or Luigi find in their adventure through Dinosaur Land during the events of Super Mario World. This level can be accessed by completing Donut Plains 4. By completing this level, the player gains access to Vanilla Dome 1. This castle is ruled by Morton Koopa Jr. The Spikes make their first appearance in this level.
The castle consists of three main rooms, a bonus area, and a boss room. The player has 400 seconds on the Timer to complete the level. This level contains no Dragon Coins in the original, but the remake has 5.
The first part is a hallway with two Thwimps. If the player has a Cape, they can fly through a gap in the ceiling located directly above the starting position. There is a pipe leading to a Bonus Area up there. After the Thwimps, there is a conveyor with three Ball 'n' Chains, and the door to the next room. The next room has lava pits, three Thwomps, and a Dry Bones.
The third and final main room consists of ledges that automatically move left and right, which the player must use to reach the top of the room. Along the way, the player has a chance to collect a cape from a ? Block. At the top, there is also a green ! Block located right before the boss door.
Once Mario has entered the boss door, Morton is shown. He seals off both sides of the room and starts battle with Mario. He starts off running at Mario, then climbs the wall and falls off the ceiling, aiming to hit Mario. Morton repeats this sequence, and everytime Mario stomps him, Morton goes faster. To defeat Morton, Mario needs to stomp on him three times. A cutscene shows Mario kicking down the castle after rescuing one of Yoshi's friends, and Mario, then, is able to access the Vanilla Dome.