This train line, technically, isn't lost as it's now a "light rail" (no, that's not a diet fad for communters).
The Port Melbourne Railway was the first significant line in Australia with the first train being locally made in just 10 weeks. Oh for that ingenuity these days !
Opening in 1854, the choo-choo chugged 4kms down the track, across the Sandridge Bridge (that gorgeous lump of metal now parading public art and cycle paths spanning the Yarra) till it reached Sandridge (that's Port Melbourne to you).
It was closed in 1987 and converted to a light rail tram way line with low-level platforms at the former stations, most of which are now privately owned.
More info HERE and HERE.