There are only nine of these in the world, and Perth is getting two of them.

Key components of one of two 600-tonne tunnel boring machines (TBM) for the Forrestfield-Airport Link, have arrived at the future Forrestfield Station. 

The 130 metre-long machine will each dig 8 kilometres of 7 metre diameter tunnels from Forrestfield Station to Bayswater, including under Perth Airport and the Swan River. 

The highly specialised machine was manufactured by German company Herrenknecht. It spent nine months in China for initial assembly and testing, and arrived at Henderson last week. 

The TBM will be craned into the dive structure at Forrestfield, and in July 2017 will begin its two-year journey underground to Bayswater where the rail line will spur off the Midland Line. 

Watch the heaviest components of the TBM, the 74-tonne cutter-head and 164-tonne front shield arriving in Perth.