Mega Metro

Early on in the construction of the $50 billion Sydney metro system, those involved face a crisis.

A 900 ton heavy drill is making a tunnel through the earth. Engineers face all kinds of problems when they realise they have to go through a minefield of pre-existing infrastructure.

A challenge lies in weight when the time comes to dig two tunnels beneath Sydney Harbour, with an insight into the team's planning process.

Architect Ross de la Motte finds out if his vision for the station design has worked out as expected. The deadline for the Northwest-line is fast approaching, and it's going to get difficult to finish everything in time.

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.