The Magical Map is the main item in the GameCube game Paper Mario: The Thousand-Year Door. If it is held above Mario on the pedastal in front of the Thousand-Year Door, it will mark the place a Crystal Star rests.
Not much is known of the Magical Map, except that a merchant supposedly found a box rumored to have a powerful map inside, but only one with a good heart could open it. When Princess Peach came to Rogueport, the merchant called Peach over. She saw the box and picked it up. When she did, it opened p and the mgical map emerged. She then sent the magical map to mario so that he may help her search for the legendary treasure of Rogueport.
When Mario first uses the Magical Map to find out where the first Crystal Star is, he automatically learns the first special move Sweet Treat.