They call it…the Object.

A mysterious mass deep under the ground in Seattle has put a stop to Bertha, the world's largest tunneling machine, and engineers are baffled.

The mostly automated Bertha is 300 feet long and five stories tall, making it the largest tunnel-boring machine on the planet. It was brought to Seattle to help with the construction of a two-mile-long, $3.1 billion highway tunnel along the city's western edge.

Bertha should be able to punch a hole through anything, and yet two weeks after first contact with the Object, engineers are no closer to knowing what stands in the machine's way.

Much like a mole, Bertha is pretty much operating blind, and engineers have been unable to get in front to see what's blocking her. “What we’re focusing on now is creating conditions that will allow us to enter the chamber behind the cutter head and see what the situation is,” said project manager Chris Dixon.

In the meantime, speculation on the Object's nature is running rampant. People have suggested everything ice age boulders to downed alien spacecraft and dragon eggs. One of the more plausible theories is that the obstruction is a piece of old Seattle, swallowed by the mucky waterfront centuries ago. “I’m going to believe it’s a piece of Seattle history until proven otherwise,” Seattle Public Library curator Ann Ferguson told The New York Times.

If the Object cannot be broken up underground, a new excavation would need to begin. Though progress has now been halted for weeks, Dixon says that work is continuing at the ends of the tunnel. The highway is scheduled to open by late 2015.

With any luck the dragons will have hatched by then and moved on.

UPDATE, January 6, 2014:

As it turns out, the object that brought the world's largest tunneling machine to a halt for weeks was just an 8-inch-diameter steel pipe. According to the Seattle Times, the 115-foot-long "well casing" was left over from a 2002 study designed to measure ground water for the Alaskan Way Viaduct replacement project.

Now comes the task of assigning blame for the pipe. According to the Washington State Department of Transportation, the well site was listed in the contract specifications sent out to bidders on the project. "I don’t want people to say WSDOT didn’t know where its own pipe was, because it did," said DOT spokesman Lars Erickson. However, Chris Dixon, project director for contractor group Seattle Tunnel Partners, says they didn't expect the pipe to be there, as well casing are normally removed after the ground water is measured.

Deputy project administrator Matt Preedy says there is no current estimate on the time and money it will take to remove the pipe and repair Bertha's cutting face.

The $1.44 billion tunnel project is now three months behind schedule.