Watch: Flying tour of Seattle tunnel

Bertha has moved on to whatever afterlife is reserved for massive mechanical marvels.

But work on the state Route 99 tunnel to replace the Alaskan Way Viaduct is still underway, with workers building the highway inside the tunnel and all the infrastructure that goes along with it.

RELATED: Timelapse video: Bertha's last bits leave tunnel

Most of the public won't get a chance to go inside the tunnel until it opens to traffic in early 2019, but the Washington State Department of Transportation sent a drone through the tunnel to give us a look at how it's progressing.

The upper roadway is more than 85 percent complete already, while the lower roadway is just getting rolling with prefabricated panels coming in next month, according to WSDOT.

From our first look at Bertha in 2012, to her latest stalls, we've watched the massive tunneling machine complete roughly 1,437 feet of the nearly two-mile tunnel. Click through here to see a timeline of Bertha's triumphs, fits and failures.

First glimpse:

December 2012 - Before we even saw the world's largest tunneling machine arrive on Seattle's shores, we got a look at her through her official Twitter account, @BerthaDigsSR99 (not to be confused with the multiple satirical Bertha accounts that have sprung up since her troubles began).

(Photo by Washington State Department of Transportation.) less From our first look at Bertha in 2012, to her latest stalls, we've watched the massive tunneling machine complete roughly 1,437 feet of the nearly two-mile tunnel. Click through here to see a timeline of ... more Photo: - Photo: - Image 1 of / 38 Caption Close Watch: Flying tour of Seattle tunnel 1 / 38 Back to Gallery

Work on the project has moved along at a consistent pace for almost two years now, but the project is still far behind schedule.

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Tunneling machine Bertha broke down in 2013 after tunneling little more than 1,000 feet into the project. Crews spent two years rebuilding the machine before work resumed in late December 2015. More problems -- a barge issue and a sinkhole behind Bertha -- halted the project in early 2016, but the contractor was able to get moving again after reforming practices that would prevent further sinkholes and other issues.

The downtime and rebuild ran up added costs for the project, costs headed for a court battle as the contractor's insurer fought to avoid paying claims and WSDOT sued to keep its options open in the future. WSDOT also went back to the state Legislature in mid 2016 to ask for more funding for the project.

In all, the project is at least 27 months behind schedule and someone (exactly which organization is still unclear vis-a-vis court battles) will wind up paying millions more than the initial costs projected for the tunneling portion of the overall project.

For now, watch the video above and take a look through the slideshow to see how the project has progressed and get an idea of where it's headed.

Daniel DeMay covers Seattle culture, city hall, and transportation for seattlepi.com. He also watches the weather like a hawk. He can be reached at 206-448-8362 or danieldemay@seattlepi.com. Follow him on Twitter: @Daniel_DeMay.