Dimensional Door

The Pure Heart Doorways are seven doors that appear on the Flipside and one door that appears on the Flopside Tower in Super Paper Mario. The Doorways appear when the according Pure Heart is placed into its Heart Pillar. Each Doorway leads to the next dimension where a Pure Heart can be found. The final Pure Heart, however, instead opens a path to Castle Bleck.

Though not important, the colors of the doors are listed below. They each correspond to the Pure Heart that spawned them, except for the final one.
 * Lineland (Chapter 1): Red
 * Gloam Valley (Chapter 2): Orange
 * The Bitlands (Chapter 3): Yellow
 * Outer Space (Chapter 4): Green
 * Land of the Cragnons (Chapter 5): Cyan
 * Sammer's Kingdom (Chapter 6): Blue
 * The Underwhere/The Overthere (Chapter 7): Purple
 * Castle Bleck (Chapter 8): Black

The first seven doors are found on the Flipside Tower. The door that leads to Castle Bleck, bigger than the other doors, is on the Flopside Tower.