World 3-Ghost House (New Super Mario Bros.)
This level is the first Ghost House in the game. The gimmick of the whole level is that there are several ? Switches placed in the different areas of the level. The ? Switches are used to reveal staircases and certain doors. However, when activated, there is a time limit, and, if the time runs out before Mario reaches the area he is supposed to go, he must go back and hit the ? Switch again.
After pressing the third ? Switch to reveal the regular exit door, Mario must instead pass by that door and go back down the large staircase to find a newly-created door. This exit leads to a Warp Cannon leading to World 6.