Ghost House

A ghost house is similar to a fortress. They are the only levels in the game that have certian ghostly enemies such as boo and eerie. There are many ghost houses in the game and almost every one has a secret exit. They are also a place where you can find Big Boo. There are 6 in total. Two in Donut Plains and one in Vanilla Dome, Forest of Illusion, Chocolate Island, and Valley of Bowser. These levels usually require much thought and fucus as rooms may lead to dead ends or doors may mislead you.

Donut Ghost house
This is the first ghost house you encounter in the game. It has two exits. One leading to the top secret area. This level has two rooms that are exactly alike which makes this a difficult puzzle to solve.