The Elizabeth Arkham Asylum for the Criminally Insane, or simply Arkham Asylum, is a psychiatric hospital located in the outskirts of Gotham City. It was founded by Amadeus Arkham in the early 20th century, transforming it from a family estate in to a treatment center.
It is dedicated to rehabilitating those considered too dangerous for normal prisons such as Blackgate Penitentiary.
The Joker's Riot
At some point, after being captured by the Batman, the Joker was transferred to Arkham where he would eventually became the patient of the then Dr. Harleen Quinzel. He would successfully manipulate her into supposedly falling in love with him and then have her give him a machine gun, allowing him to start a riot.
Around the same time, his gang overran the prison killing the guards and freed him leaving the facility in disorder in the process.
Lex Luthor's Imprisonment
Arkham was later restored from the damage caused by the Joker's riot sometime prior to 2016.
Batman, furious that Luthor had manipulated him into almost killing Superman and wanting to keep a close eye on the criminal super-genius, took the law into his own hands and had him transferred to Arkham Asylum where he could make sure the mastermind wouldn't cause any more trouble.
- Amadeus Arkham - founder
- Dr. Harleen Quinzel - psychiatrist
Originally, Arkham Asylum was used only to house genuinely mentally ill patients, having no connection to Batman or his allies, but in more recent years, it has became infamous for holding the majority of the Dark Knight's adversaries, with almost every one of them ending up within Arkham at least once.
- Babrius Aesop - A Gotham City-based criminal who used the moral lessons found in Aeosop's Fables as his MO.
- Lex Luthor - Imprisoned for committing unspeakable crimes against peace and humanity, orchestrating the Nairomi Incident and the US Capitol bombing (killing numerous people in both instances), as well as unleashing Doomsday, a monster that killed Superman and nearly brought about an apocalypse. Lex is transferred to Arkham from Belle Reve through the influence of Batman, since Lex had been declared insane therefore and unfit for trial.
- Joker - An immensely formidable criminal psychopath, top crime boss of Gotham City's criminal underworld, imprisoned by Batman for committing numerous crimes, later released in a breakout organized by Joker's gang.
- Harley Quinn - Once a psychiatrist at the Asylum, Dr. Harleen Quinzel would later become a patient at the institution herself, imprisoned by Batman for her numerous crimes, later transferred to Belle Reve.
- Killer Croc - Formidable villainous metahuman, imprisoned for his many crimes in Gotham City, most notably cannibalism. He was transferred to Belle Reve.