The Overland
Trains don't stop at Serviceton any more, to Tom Waits' lament.

Adelaide to Melbourne is about a 9 hour drive, if you do it sensibly with some stops along the way. Since this is a post about The Overland, it would be remiss of me if I didn't recommend stopping off at the long-since defunct Serviceton station to have a look around. If you're lucky, one of the caretakers might be there and show you around.
The story of Serviceton is interesting. The town sprung up around the train station that existed only because South Australia and Victoria, prior to Federation in 1901, needed to perform customs checks for passengers and goods as they moved between the two discrete colonies, so a border-station was needed. It also served as a crew change-over point until the 1980s.
Trains don't stop at Serviceton any more, to Tom Waits' lament. Give Town With No Cheer from the album Swordfishtrombones a spin. I'd give the Scarlett Johansson version a miss.

Back to the journey at hand.
It's a 9 hour drive. A one hour flight. Or a surprisingly drawn out and spatially convoluted 10.5 hour train journey. Starting in Adelaide, it wends its way up through the Adelaide Hills to Belair, following the same route (but different line) as the Adelaide Metro's Belair line. The views out over the gulf are beautiful as the train slowly (really slowly) lumbers up the hill. Once past Belair the line winds through the Belair National Park with its stunning nature.
It pops out on the plains east of the Adelaide Hills and the scenery changes. Wide horizons, and endless farmland until you get to the Murray River. The train stops at Murray Bridge for passengers, and then trundles over the bridge at Murray Bridge.
Then more broad acres. And more. And more. The views are beautiful, especially during canola season.

As the train enters western Victoria, it becomes rough. It's difficult to walk through the train carriages because of the rocking and rolling.
The scenery stays the same for most of the remainder of the journey. The train stops in the occasional town along the way, and it goes surprisingly far south, joining a line into Melbourne from Geelong.
10.5 or so hours after setting off, the train arrives in the middle of Melbourne. The journey has been mostly comfortable - the seats, even in economy, are huge with loads of leg room. There's been food to buy, decent coffee to be had.
The downsides are that, in economy at least, there are limited power outlets.
And that it takes 10.5 hours.