"Don’t act surprised, Slytherin’s are said to be as smart as the Ravenclaws, they just have an affinity to keep themselves guarded. Personally I think it’s a mixture of Fidelius and a concealment charm, the magic behind it isn’t well known so it’s likely the secret lived and died with Salazar Slytherin. There is no secret keeper so theoretically you could show anyone now you know where it is.’ Hermione shrugged. 