The One-Eyed Witch Passage is a secret tunnel that leads from Hogwarts to the cellar of Honeydukes Sweetshop in Hogsmeade. Harry Potter first learned of it from Fred and George Weasley when they gave him the Marauder's Map in 1993.
Fred and George Weasley had used the passage to sneak supplies from Hogsmeade on many occasions. When they handed on the map to Harry, Harry used it to sneak into Hogsmeade on two occasions, until he was seen in Hogsmeade by Draco Malfoy when his invisibility cloak slipped and he narrowly missed being expelled. After that he did not use the passage again.
