Stonegate

Stonegate Penitentiary appeared regularly in Batman: The Animated Series as the holding pen for Batman's enemies not headed to Arkham Asylum. This included The Penguin, Bane, Firefly, Rupert Thorne, and, presumably, Killer Croc, despite his appearance in "Trial", as part of the 'Arkham-Gang'. It first appeared in the episode "Pretty Poison", which also showed its groundbreaking ceremony in a flashback.

In DC Comics' Batman titles, Gotham's prison is Blackgate. It's not known why the name was changed for television.

Stonegate is a village south of Tunbridge Wells in East Sussex, England.