Marauder's Map

The Marauder's Map is a fictional map of Hogwarts. It is a magical map. It was created by James “Prongs” Potter, Sirius “Padfoot” Black, Peter “Wormtail” Pettigrew and Remus “Moony” Lupin. It showed the secret passages in and out of Hogwarts. The map also showed where people are by the use of named dots. The map can be viewed by saying "I solemnly swear that I am up to no good". The map can be made invisible (only the parchment will be seen) if one says "mischief managed" and taps a wand on the parchment.
The map was found by one of the Weasleys which is then handed over to Harry Potter.
This map was later used by Minerva McGonagall to help Harry Potter save his child Albus Severus Potter, in "Harry Potter and the Cursed Child."