What is the Marauders Map?
The Marauder’s Map is a magical item in the Harry Potter novels, taking the form of a map of Hogwarts which reveals the location of everyone inside the castle, along with secret passageways. Given the large scale of Hogwarts, the map represents quite a feat, especially as certain parts of the castle, such as the moving stairways, seem to change at whim. The map originally appears in Harry Potter and the Prisoner of Azkaban and plays an important role in that and every subsequent book.