The Washington Department of Transportation tunneling machine, nicknamed Bertha, is finishing its work for a new road under Seattle. The DOT posted video on Monday, April 17, showing Bertha completing final tunnel rings.

Bertha is moving to her final disassembly point, and workers are creating the concrete tunnel rings as it moves to that pit.

The machine had been digging a double-decker tunnel to house State Route 99 for nearly four years.