Slytherin Dungeon

The Slytherin Dungeon is located behind a wall in the cellars of Hogwarts School of Witchcraft and Wizardry. A password spoken to the wall is required to enter it; whereupon a passage is revealed leading to the common room -- a low-ceilinged, dungeon-like room with greenish lamps and chairs. This dungeon extends partway under the lake, giving the light in the room a green tinge. The common room has lots of low backed black and dark green leather sofas with buttons, skulls, and dark wood cupboards. It has quite a grand atmosphere, but also quite a cold one.The password to the common room changes every fortnight, and it is posted on the noticeboard.

1992
In Harry Potter's second year, he and Ron Weasley went into the Slytherin common room disguised as Vincent Crabbe and Gregory Goyle with the aid of Polyjuice Potion to attempt to discover the identity of the Heir of Slytherin. The entry password was Pure-blood when Draco Malfoy let them in. The Polyjuice Potion's wearing off prompted Harry and Ron to leave after staying nearly an hour, still not finding out the identity of the Heir of Slytherin.

1998
In 1998, Harry, operating under the alias "Vernon Dudley," attempted to defend his false claim that he was a member of the Slytherin house by describing the location of the Dungeon to the Snatchers.

Known passwords

 * Pure-Blood

Behind the scenes

 * In the video game version of Harry Potter and the Chamber of Secrets, there is another way to the common room, where there are several enemies such as Gnomes and Cornish Pixies. There is also a bridge between the Dungeons and the common room, held up by Ectoplasm. A Slytherin student casts Skurge on the Ectoplasm, so you have to find a way to restore the bridge.
 * In Lego Harry Potter, the Slytherin Common Room has underwater windows that allow one to see out into the lake.
 * Revealed in Pottermore, It was revealed that often the giant squid appears at the windows, and sometimes more interesting creatures, and that the sound of swishing water is relaxing at night-time.

Appearances

 * Harry Potter and the Chamber of Secrets
 * Harry Potter and the Chamber of Secrets (film)
 * Harry Potter and the Chamber of Secrets (video game)
 * Harry Potter and the Order of the Phoenix (video game)
 * Harry Potter and the Half-Blood Prince
 * Harry Potter and the Half-Blood Prince (video game)
 * Harry Potter and the Deathly Hallows '
 * ''Harry Potter and the Deathly Hallows: Part 2
 * Lego Harry Potter: Years 1-4
 * Harry Potter LEGO Sets

Notes and references
Salle commune de Serpentard