From the Super Mario Wiki, the Mario encyclopedia
Switch Palaces are places in Super Mario World. Throughout various levels, there are many colored outline squares called Dotted-Line Blocks. These squares can become ! Blocks by activating their respective color's ! Switch at the Switch Palaces. Switch Palaces are usually found by accessing the secret exit of an adjacent level (the only exception being the Yellow Switch Palace). A total of four Switch Palaces are accessible in Dinosaur Land. Each one of them is not playable again once it is completed.
List of Switch Palaces
Names in other languages