Central Deborah Gold Mine has to be on your list when visiting Bendigo purely because it's at the heart of the gold rush history of the city. You can book a 75 minute mining tour and go 61 metres underground via an industrial lift and see a real gold mine from the 1900s gold rush era. Explore hidden tunnels, see how 929kg of gold was extracted and the machinery and mining equipment miners once used.
It's a truly fascinating experience but I wouldn't recommend it to people who don't like confined spaces or who are afraid of the dark... you do get given helmets and torches though! You can even book kids birthday parties and functions in the mine, definitely a unique one for the history buffs!