10 Harry Potter Fan Theories Confirmed By JK Rowling

When Salazar Slytherin built his secret chamber in the bowels of the castle, it's possible that even he didn't know how long it would remain hidden or if the Basilisk inside would survive to do his bidding. How could such a place exist without a caretaker and for how long was it ever intended to be there? Although Slytherin himself left the school, fans wondered who took up the mantle in the years before Tom Riddle arrived at Hogwarts.

On Pottermore, the entry about the Chamber of Secrets explains that the line of Slytherins evolved into the line of Gaunts along the way and at least one of them, Corvinus Gaunt, secretly protected the Chamber by moving the entrance...when Hogwarts upgraded the plumbing.

The idea of a room existing without any kind of interference for a thousand years is a stretch. Yes, the Room of Requirement never turned up on the Marauder's Map, but in fairness, it wasn't always where it was supposed to be! The chamber had a set position, even if only Sytherin's heirs knew about it. And that right there is the key to its protection.

It didn't sit gathering dust until Riddle came along because the Gaunts kept it safe. They were like a line of guardians. This shows as well that there was a long family line devoted to the idea of purity at Hogwarts. In the centuries before Voldemort's rise, that little bubbling undercurrent of hate kept Hogwarts tainted, even if it was just under the surface.