Deep below Seattle's picturesque waterfront, a subterranean drama is unfolding. A five-story drill named Bertha has been carving a new tunnel as part of a $3.1 billion plan to construct a highway beneath the city. On December 6th, drilling stopped. Something is blocking Bertha. Could it be a giant boulder; a remnant of the city's glacial past? Or perhaps the shipwrecked remains of the Windward, an 18th century ship that has never been recovered? The New York Times investigates.