There’s been a lot of excitement this year about the world’s largest tunnel boring machine. Named “Big Bertha,” she arrived in Seattle in April where she is digging a 1.7-mile tunnel for the new State Route 99. The $80 million machine stands five stories tall and moves along at 3 inches per minute. Despite her size, the machine was halted recently by a mystery object with only 1,000 feet of tunnel dug. Officials say it could take up to two weeks to figure out what the obstruction is.