Super Mario World/Switch Palaces

You may have seen dotted-line "blocks" throughout the game. These "blocks" have no use in the beginning. However, if you activate a Switch Palace of the corresponding color, the dotted-line "blocks" will become solid exclamation blocks, allowing you to use them. Switch Palaces can only be completed once.

You can find the four Switch Palaces in the following worlds:

The yellow exclamation blocks will provide Super Mushrooms, the green blocks will provide Cape Feathers, and the red and blue blocks only act as barriers.