Oh! Finally a question Sophie knew! At least one of them. She raised her hand. "I know Salazar Slytherin built it." But she didn't know what for... "Um... he built it to... well, he did sound like a mysterious person, so he probably had a lot of things to hide from the others." Chamber of Secrets... to hide... his secrets! Dead ends and tunnels and everything to make things complicated. There! Nothing could be simpler!