Short answer: the Dandenong Ranges, 35 minutes east of the CBD. Cool-temperate rainforest, mountain ash trees that are among the tallest hardwoods on Earth, century-old tea rooms in Sassafras and Olinda, and the Puffing Billy heritage steam railway running on the original 1900s Belgrave-to-Gembrook narrow-gauge alignment. Most international tourists never go because nobody tells them about it; the Great Ocean Road and the Yarra Valley get all the bookings.
There are several other contenders for the “best-kept secret” title. Here are the ones that actually qualify.
The Dandenong Ranges
The Dandenongs are a forested mountain range 35 minutes drive east of the CBD. The Belgrave train (Belgrave line) runs from Flinders Street Station and connects directly to Puffing Billy at Belgrave, which means this is a fully public-transport-accessible day trip from the city. You don’t need a hire car.
What you do: ride Puffing Billy through the rainforest to Lakeside or Gembrook, walk the 1000 Steps Kokoda Memorial Track in Ferntree Gully National Park, eat scones at one of the heritage tea houses in Sassafras or Olinda, and look at the world-record-class mountain ash trees on the Sherbrooke Forest walk.
Why most tourists don’t know about it: it’s not on the Great Ocean Road tour brochures. The Yarra Valley brochures tend to focus on wine; the Dandenongs are a different proposition (rainforest, walking, tea rooms). It’s been a Melbourne weekend tradition for over 100 years; international guidebooks underweight it.
Werribee Open Range Zoo
35 minutes west of the CBD, an African-savanna-style open range zoo where you board a safari bus and drive through giraffe, rhino, zebra and antelope enclosures. It’s owned and operated by Zoos Victoria (the same parent organisation as Melbourne Zoo and Healesville Sanctuary) and is genuinely one of the best zoo experiences in the southern hemisphere — but it’s the under-promoted member of the three.
The Werribee Mansion next door (a 19th-century Italianate estate) is a separate attraction worth combining for a half-day.
The Royal Botanic Gardens at Night (Light at the Gardens)
The RBG is well-known to tourists as a daytime walk; what’s under-the-radar is the night experiences run through different seasons (Lightscape in winter, the Moonlight Cinema in summer). The Cranbourne RBG site (a separate Botanic Gardens campus 50 km south-east) is even less-visited and contains the Australian Garden — the most-developed native-plant landscape design in the country.
Coburg’s Ceres Environment Park
CERES (Centre for Education and Research in Environmental Strategies) sits on a former tip site in Brunswick East/Coburg and is now a working farm, café, organic grocer, and education centre. Saturday mornings in the café are an only-in-Melbourne experience that tourists rarely find. It’s a 15-minute tram from the CBD on route 19 down Sydney Road.
The Yarra Bend Park (and Studley Park Boathouse)
The Yarra Bend Park system runs along the Yarra River through Kew, Fairfield and Abbotsford and contains: the Studley Park Boathouse (1860s, you can hire row boats), the Fairfield Park Boathouse and Tea Gardens, the Dights Falls walking track, and a flying-fox colony at Yarra Bend that hosts thousands of grey-headed flying foxes through summer. Most tourists never realise this is 10 minutes from the CBD.
The South Melbourne Market
South Melbourne Market (1867, on Coventry Street) is the closest of Melbourne’s historic markets to the CBD bar Queen Victoria Market, but tourists rarely make it here because the QVM is the default. South Melbourne is smaller, denser, has a better dim sim (the South Melbourne dim sim is a Melbourne institution), better produce, and sits right next to Albert Park lake.
The Outer-North Day Trip: Macedon Ranges
50 km north-west of Melbourne, the Macedon Ranges contain Hanging Rock (the geological landmark made famous by Picnic at Hanging Rock, 1975), the Mount Macedon village (autumn colour rivals New England), and a developing wine region that’s the cool-climate cousin to the warmer Yarra Valley. Day-tripable, no tour buses, and at half the cost of the Yarra Valley tour packages.
What This Means for You
If you’ve got four days in Melbourne, day three should be the Dandenongs day trip rather than the Yarra Valley if you’ve already done a major wine region elsewhere in Australia. If you’ve got six days, do both — the Dandenongs as a half-day rainforest experience and the Yarra Valley as a separate winery day.
For more, see the Melbourne day trip itinerary and unique things to do in Melbourne. Parks Victoria’s Dandenong Ranges National Park visitor information is the source for the rainforest and walking-track detail.