one of the Hogwarts houses, from one of the founders, Rowena
Ravenclaw.
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Hogwarts School of Witchcraft and Wizardry was built in Scotland
by founders Godric Gryffindor, Helga Hufflepuff, Rowena Ravenclaw,
and Salazar Slytherin.
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Rocky best describes the relationship between Slytherin and the
other founders - but the other three were friends.
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It's very likely they did live in the castle as somebody has to
look after the students and there weren't many other staff members.
If they didn't live in Hogwarts they probably lived in
Hogsmeade.