Muggles' Guide to Harry Potter/Places/Chamber of Secrets

General Overview
At the time of his departure from Hogwarts, after a falling out with the other three founders of the school, Salazar Slytherin is supposed to have created a chamber, placed a monster within it, and sealed it so that only his true heir could open it. In the centuries since that time, this "chamber of secrets" has been sought many times, but never found.

Extended Description
The Chamber was in fact opened, approximately fifty years before the time of the Harry Potter series, by Tom Riddle (who later styled himself as Lord Voldemort). At that time, the monster within the Chamber, a basilisk, killed a girl (Moaning Myrtle); this put the school on the verge of closing down, because it was obviously unsafe to keep students there. The threat of being forced to leave the school was sufficient to cause Riddle to re-seal the chamber. Riddle was as fond of his "home" as Harry was. Riddle managed to frame Rubeus Hagrid and Aragog as being the Heir and the monster respectively; as the Chamber was not then re-opened, and no more victims fell to the basilisk, Riddle's version of events became accepted as fact by all except, perhaps, Professor Dumbledore.

In Harry's second year, Ginny Weasley re-opened the Chamber; however, it was not on her own that she did this. We find out in the last chapters of the book that Ginny was at the time enslaved by a "memory" of Tom Riddle. Ginny re-opens the chamber on six occasions that we are aware of.
 * When Harry is serving his detention with Professor Lockhart, he hears the voice of the basilisk.
 * On Hallowe'en, as Harry is leaving the Deathday Party, he hears the Basilisk again. Following the sound, he encounters the Petrified Mrs. Norris.
 * When Harry is in the Hospital Wing following the removal of the bones in his arm by Professor Lockhart, Colin Creevey is brought in to the Hospital Wing, Petrified.
 * Harry trips over the Petrified Justin Finch-Fletchley and blackened Nearly Headless Nick shortly after leaving the library, where he had been met with severe suspicion.
 * On his way to a Quidditch match, Harry hears the voice of the basilisk again, which prompts Hermione to head off to the library to research something. Hermione and Penelope Clearwater are Petrified as they leave the library.
 * Tom Riddle has Ginny enter the Chamber herself so that he may use her life force to re-animate himself.

Harry's final re-opening of the Chamber and defeat of the basilisk should have cleared Hagrid's name; it did secure his release from Azkaban, where he had been consigned when it was thought that he was once again opening the Chamber.

The key to opening the Chamber is Parseltongue; one must say "open" to the entrance in Parseltongue for it to open. The ability to speak to snakes has been linked to Slytherin's descendants, thus the belief that only the true heir of Slytherin can open the Chamber.

Ron and Hermione re-enter the chamber in Harry's seventh year; knowing that Basilisk venom will destroy a Horcrux, and having a Horcrux they need to destroy, Ron, who has twice now heard Harry pronounce the word "open" in Parseltongue, opens the Chamber by imitating the sound of the word. When Harry sees them, they are carrying the destroyed Horcrux and a great stock of Basilisk fangs.

According to J. K. Rowling's instructions to the film-makers for Chamber of Secrets, the chamber itself is located under the lake on the Hogwarts grounds. Owing to this fact, one must now realise where the water in the chamber of secrets originated.

Analysis
We mentioned above that it seemed that Professor Dumbledore had apparently had his doubts about whether Hagrid had been the one who opened the Chamber. We see these doubts expressed shortly after Colin Creevey is brought into the Hospital Wing. In conversation with Professor McGonagall, after examining Colin's destroyed camera, Dumbledore states that the Chamber has been opened once again. We are never told how he reached this conclusion, but it is a safe guess that something similar to the damage to Colin's camera had happened when the Chamber had been opened fifty years earlier. We note that while Dumbledore may recognize the effects, he likely does not yet know the cause. Professor McGonagall asks who has opened the chamber, to which Dumbledore responds that the question is not "who," but "how." Dumbledore does not, apparently, know where the Chamber is or how it was opened, but has come to the conclusion, either upon seeing the writing or at some earlier date, that the legend, that says the Chamber can only be opened by the true heir of Slytherin, is fact. He has also decided, possibly tentatively, that Riddle is that heir. The remaining soul of Riddle, now known as Voldemort, is believed to be in Albania, but Dumbledore knows that Voldemort's soul can ride on other people, as happened in the previous year with Professor Quirrell. Dumbledore's concern at this point is that there may be someone else, a student or teacher, who has, like Quirrell, fallen under Voldemort's spell. Dumbledore may also believe that there is some other denizen of the school who is able to open the Chamber, but that seems less likely.

A key point in this book is the ability to speak to snakes. Parseltongue is widely believed to be a marker of Slytherin forebears. As a result, Harry is believed to be an heir of Slytherin once it is revealed that he can speak to snakes. This is exacerbated by the fact that Harry is unsure of his ancestry; he cannot ask his parents if there is any chance he was descended from Salazar Slytherin. However, as Parseltongue is assumed to be a hereditary Slytherin ability, it only makes sense that the Chamber created by Slytherin would open when addressed in Parseltongue.

Questions

 * 1) We are told that Salazar Slytherin lived a thousand years or so ago, and presumably created the chamber then. While castles of the era did have interior toilets ("garderobes") in the Muggle world, indoor plumbing first appeared in England barely two hundred years ago. Suggest a reason that the mark of Slytherin, that opened the passage to the Chamber, could have been placed on a faucet. Could it be a clue for the heir of slytherin?

Greater Picture
As mentioned, only a Parselmouth can open the Chamber, and it is widely believed that the ability to speak Parseltongue is only passed to the heirs of Slytherin. As an heir of Slytherin, Tom Riddle could certainly be expected to speak Parseltongue, and so he is able to open the Chamber. Harry, with a piece of Tom's soul, is equally able to speak the language, and apparently Dumbledore has learned it, although Dumbledore did not try to find the Chamber. One must wonder why he did not; as a teacher at the school the first time the Chamber was opened, he must have had all the clues that Harry was working with. Perhaps he did not learn Parseltongue until much later in his life, and time had made the need to find the Chamber less pressing.

Ron and Hermione later managed to open the Chamber; in need of something to destroy the cup Horcrux, they visited the Chamber to retrieve some Basilisk fangs, which apparently still had sufficient venom to destroy the Horcrux. Ron had been present at Harry's initial opening of the Chamber, and when Harry opened the locket Horcrux, another artifact of Slytherin's which would open only when addressed in Parseltongue, and simply parroted the sounds Harry had made to open the locket, in order to open the Chamber.