Castlemaine's best sights are close enough to make a relaxed walking day. The art museum, Buda, the gardens, the old gaol hill, and the main-street heritage buildings tell the story of a town that grew rich quickly and then found a more creative rhythm.
If you have more time, ride the Victorian Goldfields Railway to Maldon or follow the local walking tracks around the dry hills. Castlemaine rewards wandering more than checklist sightseeing.