Melbourne is bursting at the seams, with almost five million people and although we held on to to the trams, many useful train lines were lost throughout last century and in recent decades.
The Hipster Connection
The Inner Circle served the inner-northern suburbs of Parkville, Carlton and Fitzroy. It did a beautiful job of connecting the radial train lines of Melbourne. The last part was officially closed in 1981.

The lost Inner Circle. Credits: Marcus Wong Wongm, Wikipedia.
A Really Short Trip
The Kew railway line was opened in 1887 and ran to Hawthorn (only a few kilometres). It was closed in 1957 after a long decline.
An Even Shorter Trip
The Mont Park railway is a former branch line from the Hurstbridge line that travelled one station between 1911 and 1964.

Travel one station to Mont Park. Credits: User PalmerEldritch
The Eastern Connection
The Outer Circle was built in 1891 and connected Kew, Camberwell, Burwood, Malvern and more stations. It also linked several of the Eastern radial lines. In only a few years, it faced serious financial troubles.

1884 article about the Outer Circle. Credits:https://trove.nla.gov.au/newspaper/article/6059267
A Rail Line to Call His Own
The Rosstown Railway was a private railway in the south-eastern suburbs that connected Elsternwick and Oakleigh (bridging both lines). It was built by William Murray Ross with the intention of transporting sugar beet to his sugar mill, but was eventually dismantled in 1916.

The Private Rosstown railway. Credits: Wikipedia, User: Wongm
A Train by the Beach
The St Kilda to Windsor railway line was a short trip that barely lasted a few years in the early 1860s.
A Train You Don't Want to Be On
The Spring Vale Cemetery railway line want to Necropolis station. It was open until 1951.
References:
https://en.wikipedia.org/wiki/Inner_Circle_railway_line
https://en.wikipedia.org/wiki/Kew_railway_line
https://en.wikipedia.org/wiki/Mont_Park_railway_line
https://en.wikipedia.org/wiki/Outer_Circle_railway_line
https://en.wikipedia.org/wiki/Rosstown_Railway
https://en.wikipedia.org/wiki/St_Kilda_Windsor_railway_line
https://en.wikipedia.org/wiki/Spring_Vale_Cemetery_railway_line
https://en.wikipedia.org/wiki/List_of_closed_railway_stations_in_Victoria