Mega Metro

An extension is now underway to get people the rest of the way into the centre of Australia's biggest city, including a new tunnel crossing deep under Sydney Harbour.

With the construction of Australia's biggest public transport project in full swing, we head back under Sydney Harbour and witness the historic completion of the twin metro rail tunnels deep below the surface.

With 30 kilometres of tunnelling finished, it's time to start building railway stations, laying tracks and testing driverless trains.

After a decade of planning, construction and testing, the moment of truth arrives: the biggest transport infrastructure project in Australian history is nearly complete.