Mega Metro

The inside story of a crack team building a metro system costing $50 billion.

The team embarks on the next massive challenge boring beneath a 230-year-old city where all manner of obstacles await.

A super challenge looms perhaps the greatest of the entire project - digging two tunnels beneath Sydney Harbour.

The deadline to complete the North West Line rapidly approaches; the rush is on to fit out the Skytrain viaduct and new tunnels with tracks and cabling.

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

As Australia's largest transport project gets underway, we go back under Sydney Harbour to check out history in the making as the construction of the twin metro rail tunnels continues deep under the surface.