The project will include five new underground stations in a bid to end traffic chaos in one of the world's most famous cities.
Major cities across the world face issues with congestion on their public transport networks.
Rush hour brings tens of thousands of commuters into city centres each morning - with trains, buses and roads all often packed as people make their way to work.
A new major infrastructure project in Australia, set to open in 2025, aims to ease congestion in one of the country's biggest cities.
Work on the Metro Tunnel, in Melbourne, started in 2018, with the overall project set to cost up to £5.8bn.
The project includes twin tunnels, each 5.6 miles long - as well as five new underground stations.
The tunnel will help connect a number of existing commuter railway lines in the city, which it is hoped will make using public transport in the city earlier.
The scheme is set to add additional capacity to the system, meaning trains will be able to run more frequently.
It is estimated the work will give the network capacity for an extra 39,000 people every peak travel period.
It is also thought the tunnel will ease crowding on the city's St Kilda Road and Swanston Street - currently one of the busiest tram routes in the world.
And the new tunnel may not be the end of tunnel digging in the Victoria city.
The proposed Melbourne Metro Tunnel 2, known locally as Metro 2, would link up more commuter lines via the city centre - however no work has started on this project.