Location from harry-potter-chamber-of-secrets by
A hidden underground chamber deep beneath Hogwarts, built by Salazar Slytherin a thousand years ago and accessible only by speaking Parseltongue -- the lair of the Basilisk and the place where Tom Riddle waits with Ginny Weasley's dying body.
The Chamber of Secrets is Slytherin's final argument in a debate he lost a millennium ago. He built it in secret beneath the school, placed within it a Basilisk only his bloodline could control, and left it as insurance against the Muggle-born students the other founders insisted on admitting. Tom Riddle opened it fifty years ago through Ginny's ancestor connection and killed Moaning Myrtle. Now his diary-shade has opened it again through Ginny, who has been losing time, waking with rooster blood on her hands, and painting threatening messages on the walls without remembering. The Chamber is where the final confrontation takes place: Tom Riddle, growing solid as Ginny fades, reveals his true identity, sets the Basilisk on Harry, and watches with a prefect's smile as a twelve-year-old boy faces a sixty-foot serpent alone. Fawkes arrives with the Sorting Hat. The Sword of Gryffindor appears. Harry drives a Basilisk fang through the diary. The chamber floods with ink like blood.
A long, dimly lit subterranean hall lined with towering stone pillars carved with intertwining serpents. Green-tinged torchlight casts writhing shadows. The floor is damp and black. At the far end, a massive stone face of Salazar Slytherin rises from the wall, its mouth the passage from which the Basilisk emerges. The circular entrance in Moaning Myrtle's bathroom spirals down a long pipe to reach it.
Also known as: the Chamber of Secrets, Chamber of Secrets, Slytherin's chamber