60 feet under downtown Seattle, something’s buried and it’s now obstructing the path of Bertha, the world’ biggest boring machine, in the middle of digging a tunnel to replace Highway 99’s Alaskan Way Viaduct.

There’s nothing like a mystery to get people’s imagination going. 60 feet under downtown Seattle, something’s buried and it’s now obstructing the path of Bertha, the world’s biggest boring machine, in the middle of digging a tunnel to replace Highway 99’s Alaskan Way Viaduct.

Costing about $4 billion, the 4-lane tunnel project is planned to run nearly 2 miles and be completed by 2015’s end. However, Bertha’s already run into a few delays, including union picketing and a sinkhole.

Now 1,000 feet after starting, Bertha remains stopped underground after experiencing “unanticipated and increasing resistance.” Experts are trying to identify what the natural or manmade blockage might be, and whether they should dig it out or have Bertha go through it.

For something to stop the $80 million machine equipped with a five-story tall cutter head and created specifically to crush boulders has many people posting their suspicions online.

Jokes include a UFO or Jimmy Hoffa while more serious guesses ranged from an old train or ship to evidence of a manmade island or the supernatural. As local business owner Johnnie Stroud speculated, “There are all types of ghost tours stuff down here; I am hoping that we are not disturbing something that will bring the wrath of something awful.”