Built in 1841, this forbidding bluestone prison was in operation until 1929. It's now one of Melbourne's most popular museums, where you can tour the tiny, bleak cells. Around 135 people were hanged here, including Ned Kelly, Australia's most infamous bushranger, in 1880; one of his death masks is on display. Visits include the Police Watch House Experience, where you get 'arrested' and thrown in the slammer (more fun than it sounds).
The dire social conditions that motivated criminals in 19th-century Melbourne are also highlighted, including the era's obsession with phrenology. During school holidays you can visit the Old Magistrates' Court, where notorious gangster Squizzy Taylor stood trial.
You can also join one of three creepy night tours: A Night in the Watch House, the Hangman's Night Tour or Ghosts? What Ghosts! (all $38, check the website for the schedule). The latter two are not recommended for children under 12, while the pitch-black Watch House tour isn't recommended for under 16s.