Not many of the world's biggest builds take place on two separate continents. But this 57.5-foot-diameter tunnel-boring machine was constructed in Japan and then hauled across the Pacific Ocean to the Port of Seattle, where it was reconstructed in July in its launch pit. North America's largest-ever tunnel boring machine is now digging a highway tunnel under downtown Seattle. The 7000-ton Berthais 326 feet long, giving it plenty of power to churn dirt well into 2014.