<P> The film's depiction of the Chamber has snake heads in place of the pillars and Slytherin's statue is only his head . Rowling reveals in the book Harry Potter Page to Screen; The Complete Filmmaking Journey that the Chamber has flooded since its creation under unknown circumstances . </P> <P> There are usually seven secret passages in and out of the school, and in addition, the series describes the use of twin vanishing cabinets to create another . Filch knows of just four of these while the Marauders (Remus Lupin, Peter Pettrigrew, Sirius and James) and the Weasley twins know of all seven, though where some lead is unknown . The Room of Requirement may, on occasion, create an eighth passage out of the school . The only known instance of this occurring is a passage to the Hog's Head bar that formed before the Battle of Hogwarts . Due to the nature of the Room of Requirement, it is possible that several passages to different locations could be accessed from the Room . The three passages out of Hogwarts that Filch does not know about are: </P> <Ul> <Li> A passage beneath the Whomping Willow, leading to the Shrieking Shack . </Li> <Li> A passage behind a mirror on the fourth floor, which is caved in . It led to Hogsmeade, but where in Hogsmeade it leads to is unknown . </Li> <Li> A passage beneath a one - eyed witch statue by the stairs to the Defence Against the Dark Arts classroom, leading to the cellar of Honeydukes . Speaking aloud the word' Dissendium' to the witch allows access to this passage; the hump on the statue then opens and reveals the hidden passageway . </Li> </Ul> <Li> A passage beneath the Whomping Willow, leading to the Shrieking Shack . </Li>

What are the characteristics of the hogwarts houses