Hogwarts School of Witchcraft and Wizardry was built on top of the severed head of the giantess Medusa. Her hair was snakes and once a generation her snaky hair grew upward through the plumbing to turn students to stone.

Rubeus Hagrid the half-giant was one of the only students to find the Chamber of Secrets, and snuck down there a lot to talk to her. "I haven't made any friends," he confessed. "I don't know if I'm cut out to be a wiza...rd, not being all human and all."

She giggled, and all the snakes of her hair giggled. "Okay dear, I want to tell you that a school of Witchcraft-and-Wizardry makes no sense, because those are two very different things. You're not going to make it as a wizard, or a witch. You have a different calling. Hagrid, this school needs more monsters."