Carrot Castle is a large regal castle situated in a secluded pine forest in the Mirror World. The level starts off in the forest surrounding the castle, and later takes place inside the vast castle itself. Parasol comes in handy at later most parts of the level due to the heavy winds and spike traps on the castle's roof. Carrot Castle is much like Moonlight Mansion except it has more treasure chests and secrets. The exterior of Carrot Castle is a vibrant yellow-orange with teal trim and architecture, while its interior is lit by candlelight and has slick marble flooring. Its roof has many onion domes and tall spires. Mega Titan resides here and acts as its boss.
There is an air canal right in front of the castle with a switch right up front that connects to Radish Ruins. The castle is also situated beside Peppermint Palace, making for easy travel between the two levels.
Moonlight Mansion is a spooky mansion under perpetual moonlight next to Rainbow Route. Its dilapidated outside is home to overgrowing vines, but its inside is well-lit and well-kept with shelves full of books and corridors equally full of enemies.
Both Carrot Castle and Moonlight Mansion share the same musical theme.
In the in-game map of the Mirror World, as well as the map of itself, Carrot Castle is shown to resemble St. Basil's Cathedral, a landmark of Moscow, Russia.