In the world of J.K. Rowling's Harry Potter series, Azkaban is the wizarding prison that is equivalent to the Supermax prison in Colorado. The wizards who do the worst crimes are sentenced to go there for a set amount of time, up to and including the time of their death.
The massive triangular stone fortress itself is situated on an island off of Great Britain that appears on no maps, muggle or wizard. The island is protected by many charms and spells, including Unplottable. It was built in the fifteenth century and had always had an infestation of Dementors, which were used as the prison guards for hundreds of years.
There is a small graveyard on the island for prisoners who died while incarcerated. Since 1717, the use of any of the three unforgiveable curses on another human warranted a life sentence. After the Second Wizarding War the dementors, who had joined forces with Lord Voldemort, were replaced with specially trained Aurors.
Iron Noder 2017