Chamber of Secrets

From Hpwiki

The Chamber of Secrets is a legendary secret chamber deep under the Hogwarts lake. Created by Salazar Slytherin. Can only be accessed by speaking in Parseltongue. Harry and Ron discovered the entrance to the chamber in the book of the same name. Located in the girls bathroom where Moaning Myrtle haunts, Harry found a silver serpent on the side of one of the taps on the sink, which parted to reveal a large pipe which leads down into the chamber. It was the home of Slytherin's Basilisk until its confrontation with Harry. Re-opened by Tom Riddle twice, once in person, and once via the possession of Ginny Weasley who was instructed by a diary which Tom had preserved his sixteen year old self in its pages. This is later to be revealed as one of Lord Voldemort's horcruxes. And also later enter by Ron and Hermione while trying to find something to eliminate the Horcruxes. Ron accesses it by repeating what harry had said to the chamber last time the entered it in Parseltongue "open"