Muggles' Guide to Harry Potter/Places/Azkaban

General Overview
Azkaban is the wizard prison.

Extended Description
Azkaban is a horrendous place, where Sirius Black, along with many Death Eaters, were imprisoned after Lord Voldemort fell from power. Guarded by the hideous dementors, it is located on a remote island and is virtually escape proof. According to Remus Lupin, it is a "fortress... set on a tiny island, way out to sea, but they don't need walls and water to keep the prisoners in, not when they're all trapped inside their own heads, incapable of a single cheerful thought. Most of them go mad within weeks." Sirius Black is the first person known to have escaped unassisted. Although several Death Eaters also later escaped, it is believed they were able to escape only because the dementors had deserted the prison, having been promised richer feeding if they became loyal to Lord Voldemort.

The first mention of Azkaban is in Harry Potter and the Philosopher's Stone, when it is mentioned only in passing. In Harry Potter and the Chamber of Secrets, we are properly introduced to the nature of the place, when it is decided by the Ministry that Hagrid, who was accused of opening the Chamber fifty years earlier, was responsible for opening it again. When the decision to send him to Azkaban as a preventative measure is announced, we see Hagrid's fear of the place, and later his relief at being released from it. However, the full nature of the place is not fully explained until the events of the third book, Harry Potter and the Prisoner of Azkaban.

From there, it is mentioned in passing, as people are arrested and sent to Azkaban, and as people break out. By Harry Potter and the Half-Blood Prince, the reader may begin to feel, correctly as it turns out, that Azkaban should be fitted with revolving doors.

Past and Present Prisoners of Azkaban

 * Sirius Black - arrested for the murder of Peter Pettigrew and twelve Muggles, imprisoned without trial, escaped
 * Crabbe - arrested after the Battle at the Ministry
 * Barty Crouch Jr. - arrested shortly after the initial disappearance of Voldemort, for the torture of Alice and Frank Longbottom
 * Antonin Dolohov - arrested during or after Voldemort's first reign, escaped after the Dementors left Azkaban, returned to Azkaban after the Battle at the Ministry, escaped.
 * Percival Dumbledore - arrested for attacking Muggles
 * Mundungus Fletcher - arrested for impersonating an Inferius
 * Marvolo Gaunt - arrested for attacking an officer of the Ministry, completed sentence, died shortly after.
 * Morfin Gaunt - arrested for attacking an officer of the Ministry and cursing a Muggle, released, re-arrested for murder of the Riddle family, died in prison
 * Rubeus Hagrid - arrested and held without trial on suspicion of being the person who released the Monster in the Chamber, released
 * Jugson - arrested after the Battle in the Ministry
 * Igor Karkaroff - arrested during Voldemort's first reign, plea-bargained for a shorter sentence, presumably released
 * Bellatrix, Rabastan, and Rodolphus Lestrange - all arrested shortly after the initial disappearance of Voldemort, for the torture of Alice and Frank Longbottom, all escaped. Rodolphus and Rabastan were sent back after the battle at the Ministry.
 * Walden Macnair - arrested after the Battle at the Ministry
 * Lucius Malfoy - arrested after the Battle at the Ministry, escaped
 * Mulciber - arrested during Voldemort's first reign, escaped. Was sent back after the Battle at the Ministry.
 * Nott - arrested after the battle at the Ministry
 * Sturgis Podmore - arrested for trying to get through a sealed door at the Ministry, sentenced to six months
 * Augustus Rookwood - arrested for passing secrets to Voldemort in his first reign, on information from Karkaroff; escaped after the Dementors left Azkaban, returned to Azkaban after the Battle at the Ministry, escaped
 * Stan Shunpike - arrested for boasting about being aware of Death Eater secrets, escaped
 * Travers - arrested in Voldemort's first reign, escaped
 * Dolores Umbridge - arrested after the Second Wizarding War for horrible mistreatment of Muggles

Analysis
Quite clearly, the first thing one must do when you imprison a wizard is to confiscate his wand; a wizard with a wand is as well-armed as a Muggle with a gun, and significantly more capable. Yet wizards do have some ability to perform magic without wands; we see Harry do so on a number of occasions, when his tension is particularly high. We also believe Apparition does not require wands. There are evidently spells that can prevent Apparition, and of course those must be set on the prison proper. That does leave the possibility of an escape being carried out by a Wizard or Witch who does wandless magic when very tense. This may be the rationale for the Dementors: by damping all good feelings, it may be impossible for the prisoners to become agitated enough to perform wandless magic. Despite all these safeguards, however, it is certainly possible for a witch or wizard to break out of Azkaban; Dumbledore has stated that he could break out of Azkaban if he was imprisoned, and large numbers of Death Eaters do so on two known occasions, though it must be noted that both of these major breakouts occurred after the Dementors had abandoned Azkaban to enter Voldemort's service, and that Dumbledore is a wizard of extraordinary skill. (Though even he might have overestimated his capability.)

One does rather feel that the use of Dementors is a bit excessive, however. You do not rehabilitate an evil wizard by driving him insane. However, we must also note that the entire penal situation in the Wizarding world seems a bit excessive, as people are imprisoned for lengthy periods without benefit of trial — Rubeus Hagrid, for instance, is imprisoned for some months on suspicion alone, and Sirius Black is imprisoned for twelve years without a trial. Granted that this situation may have sprung from adversity, and have been done in reaction to the appearance and activities of Voldemort, still one would think that with the threat abated, the use of Azkaban might fall off. That does not seem to happen, however.

Greater Picture
We find out in Harry Potter and the Prisoner of Azkaban that the Animagus transformation does not require a wand, as Sirius is able to transform when he is incarcerated and thus wandless. We believe he was able to escape because he was an unregistered Animagus; presumably, there is some way to prevent the transformation that would be used on an incarcerated registered Animagus, likely a variant of the unnamed spell that Sirius and Lupin used to unmask Peter Pettigrew. However, as there are so very few Animagi in existence, it may have been considered unnecessary to provide for their being incarcerated.

As mentioned, the use of Azkaban as a deterrent in the series seems to be excessive; it is only after Voldemort's second fall, and the accession of Kingsley Shacklebolt to the position of Minister for Magic, that the penal system is returned to what it should be. J.K. Rowling mentioned, in one of the interviews she gave after the release of Harry Potter and the Deathly Hallows, that after Voldemort's death, one of the things Kingsley Shacklebolt does as Minister for Magic is to retire control of Azkaban from the Dementors. This is part of what makes the magical world in the epilogue of the book "a sunnier one".