Azkaban Prison

Azkaban is a wizard's prison located on an island in the middle of the North Sea. Presumably, it only serves the magical community of Great Britain, as there are other wizarding prisons elsewhere such as Nurmengard. Using certain Charms, the prison is hidden from the muggle world, and is unplottable. It gained a reputation as a horrible place, given that its former guards, Dementors, cause great suffering to those in their proximity; most prisoners eventually went insane and slowly died under their influence. Since 1717, using any of the three Unforgivable Curses on another human being has carried a punishment of a life sentence in Azkaban (unless there is sufficient evidence that the caster did so under the influence of the Imperius Curse).