Tunnel Boring Machine (TBM) Mum Shirl has now finished work, breaking through a wall of rock at the new Barangaroo Station.
The creation of the Barangaroo Station site took about two years and involved excavating 460,000 tonnes of rock.
The only tunnel left to be created for the Sydney Metro is the second railway tunnel underneath Sydney Harbour.
Mum Shirl started work at Marrickville in November 2018. It took around 14 months for the TBM to build an 8.1-kilometre tunnel to Barangaroo, cutting through sandstone and shale.
Around 821,000 tonnes of rock, enough to fill 126 olympic swimming pools, was excavated.
The twin metro tunnels between Chatswood and Sydenham, under the harbour, will be 31 kilometres in total and around 29.5 kilometres has already been completed.
So far more than 8400 people have worked on the Sydney Metro tunneling project between Chatswood and Sydenham. The tunnelling works have employed around 560 tunnellers including carpenters, mechanical fitters, electricians and boilermakers.