As the name says, it’s an old gaol in Melbourne.
The town’s original jail, most of it was knocked down or incorporated into the neighbouring RMIT university back in the 1920s. In its 90-year existence, 133 people were hanged at the Gaol, most famously the bushranger Ned Kelly.
Today it’s a museum to colonial-era justice with extensive law and order exhibits on display. Some people claim that it’s haunted (of course) and the after-hours Hangman’s Tour cannot be recommended highly enough.