At least some content in this article is derived from information featured in Harry Potter: Hogwarts Mystery. Spoilers will be present within the article.
A common room was a shared lounge area in Hogwarts School of Witchcraft and Wizardry. There was one for each House. The common rooms featured fireplaces and sitting areas and were decorated in house colours. They were often used to do homework and to socialise with housemates. The boys' and girls' dormitories were also attached to the common rooms, with spells in place to prevent male students from entering the girls' dorms, but not vice versa, which Ronald Weasley felt was unfair.
The four Houses each had a protective measure to prevent students from other houses entering. To enter the Gryffindor Tower and the Slytherin Dungeon, one required a password. The Ravenclaw Tower required the answer to a riddle in order to enter, and the Hufflepuff Basement required tapping the barrel 'two from the bottom, middle of the second row' in the stack of barrels near the kitchen corridor, in the rhythm of Helga Hufflepuff.
It can be said that the methods of gaining entry to each house's common room mirrored the perceived intellectual reputation of each house. Hufflepuff, often known as the house with no certain particular aptitude in its students, had a very simple method of entry that never changed. On the other end of the spectrum, Ravenclaw, a house prizing intelligence, provided a new intellectual challenge with each attempted entry.
- "Why are they called Common [sic] rooms when only people from a certain house can go into them? Doesn't that make them uncommon rooms?"
- — A Ravenclaw student reflects on the name "common room"[src]
- Gryffindor Common Room — located in Gryffindor Tower, through the Fat Lady's portrait.
- Hufflepuff Common Room — located in Hufflepuff Basement, below ground level behind a stack of barrels near the kitchens.
- Ravenclaw Common Room — located in Ravenclaw Tower, beyond a bronze eagle-shaped knocker that poses a riddle.
- Slytherin Common Room — located in Slytherin Dungeon, below ground level beyond a stone wall.
Behind the scenes
- Hufflepuff was the only House to have a defence mechanism for the common room. If someone tapped the wrong barrel or the wrong rhythm, they were doused in vinegar.
- The location of common rooms other than one's own was generally secret to Hogwarts students. Harry Potter learned of the location of two common rooms other than Gryffindor's only through extraordinary circumstances — the usage of Polyjuice Potion to transform into Gregory Goyle in his second year to follow Draco Malfoy to the Slytherin common room and by consent of Luna Lovegood to the Ravenclaw common room to observe a model of Rowena Ravenclaw's diadem just before the Battle of Hogwarts. When Harry, Ron and Hermione were snatched by Fenrir Greyback's Snatcher gang, Harry replied "Slytherin" when asked what House he was in at Hogwarts. Scabior stated that it was funny how everyone thought that was what they wanted to hear, but nobody they had snatched could tell them where Slytherin's common room was. Harry's correct answer nearly saved him and the others, until Hermione was recognised from a photo in the Daily Prophet.
- Originally, Rowling intended Harry Potter to visit all four House common rooms, but he only visited three - Gryffindor, Ravenclaw and Slytherin.
- Harry Potter and the Philosopher's Stone (First appearance)
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